Documentation

How to use RentStack in the web app and Chrome extension, rental comparables, and how your inputs turn into metrics and projections. The same calculator runs in the Rental Tool and in the extension sidebar.

Using the app

RentStack helps you model a rental property: financing, income, expenses, and long-term returns. You need a free account to use the Rental Tool. For plan limits (sessions, calculator runs, saves, and AI chat), see the FAQ and Pricing.

Rental Tool

Sign in, then open Rental Tool from the header.
On the Tools landing page, click Start a report to begin a new analysis. On the free plan, each new report started from here counts as a session.
Enter purchase price, rent, taxes, insurance, loan terms, and other assumptions—or paste a property listing link, use the Chrome extension on a listing page to model and save from the sidebar. In the Rental Tool on Advanced, use Get estimate next to Unit 1 rent when market rent estimates are enabled; then open See rental comps after a successful run.
Open the full results to run the calculator. Recalculations after you change inputs count as calculator runs on the free plan.
On Basic or Advanced, save reports from the analysis flow and find them under Saved reports. You can share reports with teammates, collaborate on shared reports, and compare listings from the Collaborations experience (invite team members from Home).

Saved report retention

Saved reports are kept while you use them. If a report has not been updated for 12 months, RentStack removes it automatically. The timer is based on when the report was last saved (inputs, notes, chat, and similar).

Opening or viewing a report alone does not extend retention—you need to save changes to reset the timer. Expired reports disappear from Saved reports; bookmarked links to an old report ID will no longer load. To keep a deal long term, open it and save an edit at least once a year, or export a PDF while it is still available. You can delete reports anytime from Saved reports.

Other tools

From the same Tools area you can open the Closing cost calculator, What-if loan, and Rent estimator. The floating assistant can answer questions and search the web when that feature is turned on for your environment.

Chrome extension

RentStack can be opened from the Chrome extension and is fully supported on real estate listing sites. Sign in to pull the listing address and price, run the same rental analysis as the Rental Tool, and view outputs—all without leaving the listing. On paid plans, you can save reports from the sidebar. Always verify the address and your inputs.

Getting the extension

Install RentStack from the Chrome Web Store.
Click the RentStack icon to open the extension on any page. On supported listing sites, a sidebar also appears on the right; use the tab on the edge of the page to collapse or reopen it. Your open/closed preference is remembered for that browser session.
Sign in from the sidebar when prompted. Use Google, Apple, Facebook, or Microsoft—only the provider's sign-in window opens.

Supported sites

The extension supports these listing sites:

Zillow
Redfin
Realtor.com
Trulia
Homes.com
Apartments.com
Apartment List
Rent.com
Rentals.com
ForRent.com
HotPads
Zumper
LoopNet
Crexi
Movoto
Compass
Coldwell Banker
Century 21
RE/MAX
Keller Williams
Sotheby's International Realty
Properties.com
StreetEasy
Land.com
LandWatch
Realtor.ca
Rightmove
Domain
realestate.com.au
HAR.com
MLS.com
Homesnap
Opendoor
Offerpad
Rocket Homes
HomeFinder
Point2Homes
Listanza

Plans in the extension

Free (signed in): Use Inputs and Outputs: enter assumptions, run Analyze, and read cap rate, cash flow, DSCR, and related metrics in the sidebar. Each Analyze uses one report session and one calculator run toward your free monthly limits (10 sessions and 100 calculator runs—see the FAQ). A usage bar under the workspace shows your session count for the current month.
Basic or Advanced: After you analyze, use Save to RentStack on the Outputs tab to create a saved report in your account, then See report to open it in the Rental Tool.
Advanced only: Rent comps tab (market rent estimate and comparable rentals), Chat (AI assistant for the listing), and automatic rent (and insurance when purchase price is set) when you use price pick.

Sidebar layout

The header shows the listing address when RentStack can read it from the page. Click the RentStack logo to open the main app. Along the right edge, icon buttons switch views:

Inputs — purchase price, rent, taxes, insurance, financing, and operating assumptions.
Outputs — results after Analyze.
Rent comps — rental comparables (Advanced only).
Chat — ask questions about the property (Advanced only).

At the bottom of the rail: Documentation (opens this page) and your profile menu (Profile, Sign out).

Load a listing from the page (price pick)

The price picker is the fastest way to start: hover a listing price on the page and click the RentStack control to pull data into the sidebar.

Sign in and open the sidebar on a supported listing site. Hover a listing price on the page (detail page or map/search card). A small RentStack control appears on the price.
Click that control. RentStack fills purchase price and default closing costs (3.5% of purchase price if you leave closing blank), reads the address from the page (or near that price on map views), and—when you are signed in with a purchase price—estimates property tax (county effective rate) and insurance. Your profile defaults for financing and operating assumptions are applied too. On free and Basic, price pick only populates Inputs—tap Analyze when you are ready (free plan: each Analyze uses one session and one calculator run). On Advanced, RentStack also runs the calculator automatically and switches to Outputs after loading.
On Advanced, price pick also fetches a market monthly rent estimate and loads the Rent comps tab. A short loading state may appear while estimates run.
Adjust any field on Inputs if needed, then tap Analyze (free and Basic), or review Outputs on Advanced after price pick.

You can also type values manually without using price pick. Reset on Inputs clears listing fields (price, rent, tax, insurance, and so on) for another property; financing and operating assumptions (down payment %, loan terms, maintenance, capex, management, vacancy) are kept.

Required inputs before Analyze

These fields must be filled in before you tap Analyze:

Purchase price
Closing costs
Monthly rent
Property tax (annual)
Insurance (annual)
Down payment % (financing)

Property tax can be entered as dollars or as a percent of purchase price. Other fields (rehab, HOA, utilities, loan term, vacancy, and so on) use your defaults or zeros until you change them.

Outputs and saving

After a successful analyze, Outputs shows key metrics (for example monthly cash flow, cap rates, cash-on-cash, and DSCR). On Basic or Advanced, tap Save to RentStack to store the analysis as a report linked to this listing session. Then use See report to open the full Rental Tool with the same inputs and results.

Rent comps in the extension

On Advanced, open the Rent comps rail tab after a price pick (or whenever a rent estimate has been loaded for the current address). You will see the subject property summary and a table of nearby rental comparables—the same data partner snapshot used in the app's See rental comps flow. Column meanings are in the Rental comparables section below (the extension table matches that content; the full map view is in the web app).

After you Save to RentStack, See rental comps on report appears on the comps tab and opens the rental comparables section on your saved report in the app.

Chat (Advanced)

The Chat tab lets you ask questions about the listing and your assumptions. Usage limits apply per your plan.

Tips

If the address in the header looks wrong, refresh the listing page or enter assumptions carefully before saving.
Collapsing the sidebar gives the listing page full width; expand it again with the RentStack tab on the right.
For the full calculator UI, charts, price sensitivity, and collaboration features, open the saved report in the Rental Tool after you save from the extension.

Rental comparables

Rental comparables show a long-term monthly rent estimate from a market data partner, plus nearby rental comparables from the same result. In the Rental Tool on Advanced, click Get estimate next to Unit 1 rent to run it. In the Chrome extension, comparables load when you use price pick (Advanced) or when chat applies a rent snapshot—open the Rent comps rail tab to view them. After a successful estimate, RentStack can save the snapshot with your draft or saved report so you can reopen comparables later (including See rental comps on report from the extension after you save).

Treat the headline rent, range, and comps as starting points—verify against local listings and your own judgment. If no comparable rows come back, you may still see the subject summary and map when locations are available; a short note explains that the point estimate still applies.

If beds, baths, square footage, or property type are missing or wrong, correct them on Inputs, then click Refresh comps from Inputs on the comps view (up to three live refreshes per property). The first estimate still uses the address only so one-click analyze stays fast.

Map

When locations are available: Blue marks the subject (your analyzed address). Green numbered pins match the # column in the comparables table.

Subject summary

Text above the first table:

Address queried: The address RentStack used for this rent lookup (it may differ slightly from what you typed after standardization).
Est. rent/mo: The market model's point estimate of long-term monthly rent for your property—the same kind of value Get estimate can apply to Unit 1.
Low rent / High rent: Optional monthly range from the data partner. When they don't provide it, you'll see a dash. Not every run includes both ends of the range.

First table row (your property's attributes from the estimate, not a separate comp listing):

Bed: Bedroom count for your property when the estimate includes it.
Bath: Bathroom count when available.
Sq ft: Living area when available.
Type: Property type label (for example single-family vs apartment), as provided by the data source.
Last seen: Date the partner last associated with this property record or listing, when they supply one (formatted for easy reading).
Year built: Year built when the partner supplies it.

Comparables table

Each row is one rental comparable from the partner. Columns:

#: Row number for this comp. Matches the green pin label on the map.
Address: Address (or best location text) for the comparable.
Rent/mo: Monthly rent tied to that comparable when the partner provides it.
Last seen: Date the partner last tied to that listing or record, when available.
Similarity: How closely the partner ranks this home to yours, shown as a percentage. Higher usually means a closer match in their model; the exact method is defined by the data vendor.
Distance: Straight-line distance from your property to this comp in miles, when provided.
Bed: Bedrooms for the comparable.
Bath: Bathrooms for the comparable.
Sq ft: Living area for the comparable, when available.
Type: Property type for the comparable (same idea as the subject Type column).

Some extra details (such as listing type) may be saved in the background for future use but are not shown as columns in this table.

Calculator overview

You enter numbers in the Rental Tool (or load them from a saved report). RentStack turns that into cash flow, cap rates, debt coverage, a multi-year projection with a modeled sale, price sensitivity, and break-even figures.

Percentages are entered as whole numbers (for example, 20 means 20%). Dollar amounts are in USD.

Before we calculate

A few values are normalized from what you see on the form:

Total monthly rent — RentStack adds every unit rent you entered into one total used in the model (one unit or many).
Closing costs — If closing costs are left at zero, RentStack uses 5% of the purchase price for the analysis. Enter your own dollar amount anytime to override that.
Utilities — Operating utilities are the sum of electricity, gas, water/sewer, garbage, and other fixed monthly utility lines you entered. If that sum is zero, older single-field utility amounts may still apply in edge cases; the form normally fills the detailed lines.
PMI — Private mortgage insurance is included in the analysis when you set a PMI annual rate above zero.

Purchase & upfront costs

Purchase price: What you pay (or model) for the property. Drives loan size, cap rates, appreciation, and loan-to-value.
Closing costs: One-time fees at closing. Counts toward cash you put in up front and toward "project cost" for pro forma cap rate.
Rehab / upfront capex: Renovation or capital work before rent starts. Added to your initial cash with down payment, closing, and points.

Financing

Down payment (%): Percent of purchase price you put down. Loan amount is purchase price minus down payment (not below zero).
Interest rate (annual): Nominal yearly rate on a fixed-rate loan, converted to a monthly rate for principal and interest.
Loan term (years): How long the loan amortizes; also shapes the loan-balance chart in results.
Points (% of loan): Up-front lender cost as a percent of the loan; included in initial cash out of pocket.
PMI (annual % of loan): When enabled and your starting loan-to-value is above 80%, monthly PMI is based on the outstanding balance each month. It stops once amortization brings LTV to 78% of the original purchase price or below.

Monthly mortgage (P&I) uses the standard fixed-rate payment formula on the loan amount, your rate, and the term in months.

Income

Unit rents: Rent for each unit or segment you enter. The model uses the sum of those amounts as total monthly rent.
Other monthly income: Parking, storage, laundry, or similar. For net operating income, vacancy applies to rent first; this income is added after that. The cash-flow summary also adds it to gross income before subtracting expenses.

Operating expenses

Variable (% of monthly rent) — Maintenance, capex reserve, property management, and vacancy are each calculated as a percent of total monthly rent. Vacancy is its own line; it is not applied twice.

Fixed (ongoing) — Property tax and insurance are entered as annual amounts and split by month. HOA and utilities are monthly. In long-run projections, tax, insurance, HOA, and utilities can grow each month at the expense growth rate you set.

Net operating income (NOI), monthly — Effective gross income is rent after vacancy, plus other monthly income. NOI is that amount minus operating expenses (variable lines plus fixed lines, with fixed costs growing in projections when you model inflation).

The expense chart groups items into Mortgage, PMI, Taxes, Insurance, Variable expenses (maintenance, capex, management, vacancy), and Fixed expenses (HOA plus utilities).

Growth & projections

Rent growth (annual %): Applied smoothly month to month so a full year compounds to the annual rate you entered.
Expense growth (annual %): Inflation on fixed operating costs (tax, insurance, HOA, utilities) inside the monthly projection.
Holding period (years): How many years of operating cash flows run before the modeled sale in the final month.
Property value growth (annual %): Appreciation on purchase price for the sale: sale price ≈ purchase × (1 + growth)ⁿ over the holding period.
Selling costs (% of sale): Commissions, fees, and similar as a percent of the modeled sale price.

IRR projection — The engine still steps month-by-month: month zero is your total cash out (down payment, closing, rehab, points). Each month adds net operating income minus mortgage payment minus PMI when applicable, with rent and fixed expenses growing as above. The last month adds what you walk away with after sale: sale price minus selling costs minus remaining loan balance. For IRR, the app uses a separate annual cash-flow path: one net amount per calendar year (rent and expense growth step once per year), with net sale proceeds in the final year—IRR is solved on that yearly series (one period = one year), not on monthly IRR periods.

Outputs & metrics

Initial cash / initial investment: Down payment + closing + rehab + points—the same basis as the projection's starting outflow.
Purchase cap rate: Annual NOI divided by purchase price (NOI × 12 from the monthly model).
Pro forma cap rate: Annual NOI divided by total project cost (purchase + closing + rehab + points)—sometimes called "going-in" on all-in cost.
Cash-on-cash (estimate): A first-year-style read: estimated annual cash flow after debt and an early PMI assumption, divided by initial cash (when initial cash is greater than zero).
DSCR: Annual NOI divided by annual debt service (P&I). Not applicable in the usual way when there is no loan payment.
Monthly cash flow (summary): Gross income (rent plus other income) minus the full monthly expense stack in the breakdown (mortgage, PMI, taxes, insurance, variable, fixed).
Price sensitivity: Shows how monthly cash flow changes at offer prices above and below your base purchase. Closing costs move in proportion to price. Other inputs stay the same.
Break-even rent: The monthly rent level where estimated first-year cash flow is about zero.
Break-even offer price: The purchase price (with closing costs scaled like the sensitivity table) where estimated monthly cash flow is about zero; may be blank if no answer is found in the search range.
Loan balance / value / equity chart: Year-by-year: loan balance from standard amortization, property value growing from purchase at your appreciation rate, equity = value minus loan balance (uses loan term, not holding period).

Property metadata

Bedrooms, bathrooms, square footage, property type, and year built are saved with the report for maps, exports, and the assistant. They don't change the financial math by themselves—only the inputs you use for the analysis do.