Cash Flow Per Door: A Useful Rule of Thumb With a Dangerous Blind Spot
Learn what cash flow per door means, how investors use the $100 to $200 per unit benchmark, and why it can mislead without context.
By David Chen, Buy-and-Hold Investor · Last reviewed: August 11, 2026 · 7 min read
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Open the matching calculator and test each assumption against your own deal.
What Cash Flow Per Door Means
Cash flow per door is monthly cash flow divided by the number of rentable units, or doors. A duplex that nets $300 per month produces $150 per door. Investors use it as a quick, unit-level gut check when comparing properties of different sizes.
The appeal is simplicity. Instead of comparing a single-family house to a twelve-unit building on total dollars, per-door normalizes the number so you can scan deals of any size on the same scale.
The Formula and Common Benchmarks
Cash Flow Per Door = Total Monthly Cash Flow / Number of Units
A widely repeated rule of thumb targets $100 to $200 of cash flow per door per month for buy-and-hold rentals. Some investors demand more in higher-risk markets and accept less in strong appreciation markets.
Treat these numbers as folklore, not law. They come from a specific era of rates and prices, and a fixed dollar target ignores how much capital each door required and how much risk it carries.
Where Per-Door Breaks Down
- $150 per door on a $80,000 unit is far better than $150 on a $400,000 unit, but the metric treats them the same.
- It ignores the cash invested, so it cannot tell you your return on capital.
- It rewards cheap, high-maintenance units that produce thin but positive numbers.
- It says nothing about reserves, so a property can hit its per-door target and still be one roof away from a bad year.
- A fixed dollar target does not adjust for inflation, so $100 today is not the $100 of a decade ago.
Worked Example
Property A is a single-family rental that nets $220 per month on $70,000 of cash invested. Property B is a triplex netting $450 per month, or $150 per door, on $160,000 invested. Per-door favors Property A.
But cash-on-cash return tells a fuller story: Property A earns about 3.8% while Property B earns about 3.4%. They are closer than per-door suggests, and the triplex may spread vacancy risk across three units. Per-door pointed you in the right direction but hid the nuance.
How to Use It Well
Use cash flow per door as a fast screen and a communication shorthand, not as a final decision metric. It is genuinely useful for quickly rejecting deals that clearly cannot cover surprises.
Once a property clears the per-door screen, move to cash-on-cash return, DSCR, and reserve adequacy. Those metrics account for the capital, the financing, and the risk that per-door quietly ignores.
Frequently Asked Questions
What is a good cash flow per door?
A common benchmark is $100 to $200 per unit per month, but the right number depends on the market, the price per unit, and your risk tolerance. Always pair it with cash-on-cash return, since the same per-door figure can represent very different returns on capital.
Is cash flow per door before or after reserves?
The most honest version is after setting aside allowances for vacancy, repairs, and capital expenditures. A per-door figure that ignores reserves overstates the money you can actually keep and hides future large expenses.
Why do experienced investors distrust per-door numbers?
Because per-door ignores how much capital and risk each unit carries. A high per-door number on an expensive or high-maintenance property can represent a weak return, which is why seasoned investors treat it as a screen rather than a verdict.
David Chen · Buy-and-Hold Investor, Denver, CO
David is a long-term rental investor who manages a portfolio of buy-and-hold properties. He writes from the operator seat about expenses, reserves, and the numbers that decide whether a rental actually performs.
Educational Disclaimer
All calculations are estimates for educational and planning purposes only. PropertyFlowTools.com does not provide financial, tax, legal, lending, or investment advice. Verify calculations and consult qualified professionals before making property or financing decisions.