Rental property calculator
Cap rate and cash flow for homes you can buy today.
Type something like “rent in Cleveland under $100k”. Roommie Invest finds real homes for sale on Zillow, estimates the rent, adds the yearly costs of owning each one, and shows the cash flow a year, the cap rate and how much of your own cash it takes. Then it says whether it is a good rental, only works at a lower price, or is a skip.
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Rent
In the USA the rent is Zillow's rent estimate for that home when there is one. For a duplex it counts each unit, a little lower than the single unit figure. Without an estimate it uses the city's usual rent for a 3 bedroom home, adjusted for bedrooms and the area's price level. You can type your own rent.
Yearly costs
These come off the rent before anything else:
- Property tax: the home's last tax bill or the city's rate, whichever is higher, since many states reset the tax after a sale
- Landlord insurance by state, for the home's size
- Repairs: 8% of the rent
- Empty months: 6% of the rent
- A manager: 9% of the rent
- Savings for big repairs: 5% of the rent
Cap rate
Cap rate is the yearly rent left after these costs (net operating income), divided by everything you paid: the price, the buying costs and the repairs. A rental in the USA is a good deal at a cap rate of 7% or more with money left over each year, and “only at a lower price” from 5%.
Cash flow and the mortgage
Turn on the mortgage to see a loan with 25% down at 7% over 30 years. Cash flow is the rent left after costs and loan payments. “Your cash” is what you put in yourself: the price, buying costs and repairs, minus the loan.
Cash-on-cash return and the 1% rule
Cash-on-cash return is the cash flow a year divided by your own cash. Roommie Invest shows both numbers, so it is one division. It does not use the 1% rule. It counts the real costs instead.
A check most calculators skip
If buying and fixing a home costs more than it would sell for fixed up, rent does not save it: you lose the gap the day you sell or refinance. When the gap is over 10%, Roommie Invest warns you and gives the highest price that would make sense.
Price
Free to start: 30 home checks with a free account, or 20 homes a day without one. One home check is one real home, found and checked. After that, 500 home checks cost $15 once and never expire, or Invest Pro costs $29 a month for 2,000 home checks. The same search again within 12 hours, and any question about a home, is free.
Questions
How do you calculate cap rate on a rental property?
Take the yearly rent minus taxes, insurance, repairs, empty months and management. Divide it by what you paid in total, including buying costs and repairs. Roommie Invest shows this for every home it finds.
What is a good cap rate?
Roommie Invest calls a US rental a good deal at 7% or more with money left each year, and “only at a lower price” from 5%. In the UK, Germany and Belgium the bar is 5%.
Does it show cash-on-cash return?
It shows the cash flow a year and your own cash. Cash-on-cash return is the first divided by the second.
Where does the rent come from?
In the USA, Zillow's rent estimate for that home, or the city's usual rent when there is none. You can change it.
How much does Roommie Invest cost?
It is free to start: 30 home checks with a free account, or 20 homes a day without one. One home check is one home found and checked. Then 500 home checks cost $15 once, or Invest Pro costs $29 a month for 2,000 home checks.
Is this financial advice?
No. The numbers are estimates from listing data, public price records and local averages. Always see the home, and check the costs with a local agent, lawyer, notary or solicitor before you buy.
Updated 6 November 2026. Numbers are estimates from listings, public sale records and local averages. Not financial advice. Always see a home before you buy.