How to calculate rental-property cash flow

Start with the money you can actually collect

Rental-property cash flow is the money left after rental income pays the property’s recurring costs and financing. For planning, also set aside money for major replacements. A positive estimate means the assumptions leave a surplus; it does not establish that tenants will pay that rent or that the property is ready to buy.

Begin with scheduled whole-home monthly rent. Reduce it for vacancy and collection loss, then subtract operating expenses, principal-and-interest payments and your capital-replacement reserve. Keep the reserve visible: a roof bill does not arrive evenly each month, but ignoring it makes an average month look better than the long-term economics.

A $400,000 example, with every assumption visible

This is a hypothetical stabilized long-term rental, not an available house. Assume $3,200 monthly rent, 50% down, a 30-year fixed loan at 6.5%, 5% vacancy and collection loss, and the costs below. The interest rate, rent and cost allowances are teaching inputs, not current quotes or national averages. No mortgage insurance is assumed.

Management is 8% of collected rent with no minimum fee. Repairs and capital reserves are each 5% of scheduled rent. Leasing costs assume a fee equal to three quarters of one month’s rent every 24 months. Taxes use an illustrative 1.2% of price annually. HOA, insurance, utilities and administration are separate inputs.

Separate the payment from the property costs

A lender’s total payment may already include tax and insurance escrow. Use principal and interest as the debt line if you list taxes and insurance separately. Subtracting an escrow-inclusive payment and then the same bills again counts them twice. Conversely, an unescrowed expense still needs a line in your budget.

Our planning NOI is collected rent less the listed operating allowances, before debt payments and the capital reserve. Definitions can differ in lender and investment reports; compare the underlying line items before comparing NOI, cap rates or coverage ratios. Cash flow includes the entire principal-and-interest payment, even though principal builds equity.

Find out what would erase the surplus

The example leaves $412.66 each average month. That cushion could disappear through several smaller changes rather than a single disaster. Test a lower rent, longer lease-up, a higher insurance quote and an assessment separately, then together. A stabilized average also hides the cash needed before the first tenant moves in.

Model the actual timing on a second worksheet: closing day, make-ready work, an empty first month and the next annual insurance bill. Keep a funded reserve outside the down payment. If the purchase only works with the highest comparable asking rent, no repairs and immediate occupancy, improve the evidence before relying on the result.

• Replace illustrative rent with dated comparable evidence and a range.
• Replace the rate with an investment-property loan quote for your terms.
• Check taxes after purchase, HOA dues, rental permission and assessments.
• Budget repairs from condition and expected replacements, not photos alone.

Before-tax cash flow is not your tax result

Taxable rental income and cash flow are different. Mortgage principal and money merely set aside in a reserve are not current deductions. Depreciation is a noncash deduction; loss limitations can delay a tax benefit. IRS Publication 527 explains these distinctions. Do not add a presumed refund to the monthly surplus.

RentQuarry’s nationwide manual workspace provides before-tax planning. Its separate California illustration has a limited, disclosed tax scope; it is not a nationwide tax-return engine. These guides use before-tax numbers throughout so the examples can be compared without inventing a personal tax profile.