Cash flow is the money a rental actually puts in — or takes out of — your pocket. Start with the rent you collect, subtract operating expenses, then subtract debt service (your mortgage principal and interest). What’s left is cash flow: positive means the property pays you, negative means you feed it each month.
Cash flow differs from NOI, which stops before the mortgage, and from taxable income, which factors in non-cash items like depreciation. Setting aside reserves for vacancy, repairs, and capital expenses is what separates durable cash flow from a number that looks healthy until the first big bill lands.
Build a cash bridge for one stated period
Suppose a unit collects $2,600 in rent during a month, pays $900 of operating bills and $1,500 of principal-and-interest debt service, and assigns $250 to a capital reserve. The operational cash result before the reserve is $200; the owner-available result after the reserve policy is negative $50. Showing both prevents a transfer into savings from being mistaken for an operating expense while still acknowledging that the cash is not available to distribute.
Use actual receipts and cleared or accrued obligations for a historical report. Use explicit assumptions for underwriting. Mixing collected rent from one period, annualized taxes from another, and an aspirational maintenance allowance produces a number that cannot be reconciled or repeated.
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Name the property, bank or ledger basis, start and end dates, and whether figures are actual or forecast.
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Separate operating expenses, debt service, capital work, owner contributions, and owner distributions.
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Reconcile the historical bridge to bank activity and retain explanations for timing items.
Cash flow, NOI, and taxable income answer different questions
NOI stops before financing and many owner-level items. Cash flow includes actual debt service and other cash movements chosen for the analysis. Taxable rental income follows tax rules and can include noncash depreciation while treating mortgage principal differently from interest. A landlord should not move one figure into another report merely because the labels all contain "income."
Use cash flow to test payment capacity, reserve policy, and distributions. Use a downside version with a missed payment, repair, insurance change, or vacancy. A positive base month is not proof that the property can fund an irregular roof, turnover, or deductible.
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Editorial ownership
Written and maintained by the Aptoria editorial team
Editorial method reviewed July 28, 2026. Aptoria reviews scope, source fit, examples, limitations, links, and publication gates. This record does not claim attorney, CPA, lender, appraiser, or other independent professional sign-off.
Primary and authoritative sources
Related terms
Investing metrics
Net operating income (NOI)
Net operating income is effective property income minus normalized property operating expenses, before debt service and owner-level income taxes.
Investing metrics
Cash-on-cash return
The annual pre-tax cash flow a property produces divided by the actual cash you invested in it.
Investing metrics
Vacancy rate
The share of rental units — or potential rent — that sits empty and uncollected over a period.
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