Rental Property Cash Flow: How to Calculate Monthly Net Cash Flow
Calculate monthly and annual cash flow for any rental property. Covers gross rent, all expense categories, debt service, and what positive cash flow benchmarks look like by property type.
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What Rental Property Cash Flow Measures
Cash flow is what's left over after collecting rent and paying all expenses including the mortgage. It's the most straightforward measure of whether a rental property makes money month to month.
Monthly Cash Flow = Gross Rent − Vacancy − Operating Expenses − Debt Service
Unlike cap rate (which excludes financing) and NOI (which excludes debt service), cash flow gives the actual money in your pocket after all obligations.
The Complete Cash Flow Formula
Step 1 — Gross Rental Income All rent from all units, including any pet rent, parking income, or laundry revenue.
Step 2 — Subtract Vacancy A vacancy allowance accounts for the time units are empty between tenants. Typical rates: - Strong rental markets: 3–5% - Average markets: 5–8% - High-turnover or rural: 8–12%
Step 3 — Subtract Operating Expenses
Step 4 — Subtract Debt Service Monthly principal + interest + PMI (if applicable). This is what differentiates cash flow from NOI.
Worked Example: Single-Family Rental
A $320,000 single-family home, 20% down, financed at 7.25% for 30 years:
This property has negative cash flow — it costs the investor $593/month out of pocket. Despite this, the investor gains equity through principal paydown and may benefit from appreciation. Negative cash flow properties can still be good investments — but you must budget for the shortfall.
Cash Flow Benchmarks
The $100/door (per unit, per month) rule is a common informal benchmark for minimum acceptable cash flow in single-family rentals.
Cash Flow vs. NOI vs. Cash-on-Cash Return
Cash-on-Cash Return = Annual Cash Flow ÷ Total Cash Invested
Example: If annual cash flow is $3,600 and you put $64,000 down (20% down + closing costs), cash-on-cash = $3,600 ÷ $64,000 = 5.6%
Total Return vs. Cash Flow Return
Strong cash flow markets often have lower appreciation potential; low cash flow markets in expensive cities often have stronger appreciation. A common investor question: would you rather have $500/month cash flow that grows at 2% per year, or −$200/month that grows at 8% per year?
The answer depends on your hold period, other income sources, tax situation, and whether you have reserve funds to absorb negative cash flow. Both strategies work — but you must plan for the actual cash demands of your portfolio.
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Frequently Asked Questions
- How do you calculate rental property cash flow?
- Monthly Cash Flow = Gross Rent − Vacancy Allowance − Operating Expenses − Mortgage Payment (P&I). Operating expenses include property taxes, insurance, management fees, and maintenance reserves. NOI excludes the mortgage payment; cash flow includes it.
- What is a good cash flow for a rental property?
- Many investors target $100–$200 per unit per month as a minimum. Strong cash flow is $300–$600/unit/month. In expensive markets (coastal cities), cash flow is often negative or breakeven — investors accept this in exchange for appreciation potential. The right benchmark depends on your investment strategy.
- Why is maintenance reserve important in cash flow calculations?
- Properties require ongoing capital expenditure: roof replacement, HVAC systems, appliances, plumbing. Setting aside 0.5–1% of property value annually (or $1/square foot) for CapEx prevents a $12,000 roof replacement from devastating your finances. Without reserves, cash flow is overstated.
- Can a property with negative cash flow still be a good investment?
- Yes, in markets with strong appreciation potential. A property losing $400/month but appreciating at 6% annually in a market like Denver or Austin might produce better total returns over 10 years than a positive-cash-flow property in a flat market. The risk is that you must fund the shortfall from other income.
- How is cash flow different from profit for tax purposes?
- Very different. Mortgage principal paydown isn't deductible, but depreciation (a non-cash deduction) is. A property with $500/month positive cash flow might show a paper tax loss due to depreciation deductions. This tax efficiency is one of real estate investing's major advantages.
Last updated 7/28/2026