Common questions
How do you calculate rental cash flow?
For a simplified monthly example, start with $2,000 in scheduled rent, subtract a $100 vacancy allowance and $600 in operating expenses: NOI is $1,300. Subtract $900 in principal-and-interest payments and a $100 capital reserve to leave $300 in pre-tax cash flow, or $3,600 per year. Using the same assumptions, NOI divided by debt service gives a DSCR of about 1.44. These are illustrative inputs, not a forecast or lending quote.
For the full sequence, read how to underwrite a rental property. To compare NOI with price before financing, use the cap rate calculator.
What is DSCR and why do lenders care?
Debt service coverage ratio = net operating income ÷ annual debt service. It measures whether the property itself covers its loan payments. Many rental lenders look for roughly 1.20–1.25; below 1.0 the property doesn’t cover the mortgage from its own income. This calculator uses appraisal NOI (which excludes capex and income tax) over principal-and-interest debt service. Some lenders instead use a simpler gross rent ÷ PITIA, so a lender’s stated DSCR can differ; treat the number as context, not a rule.
Can I enter each cost yearly or monthly, or as a percent of rent?
Yes. Every recurring operating cost (property tax, insurance, flood insurance, HOA, property management, maintenance, capex reserve, vacancy, owner-paid utilities, and a misc line) has a yearly/monthly toggle, and the ones that are naturally rates (management, maintenance, capex, and vacancy) also switch between a percent of rent and a dollar amount. Enter a bill however you have it; the converted figure is shown right under each field.
What counts as operating expenses, and where do capex and vacancy fit?
Operating expenses are property taxes, insurance, HOA, management, maintenance and similar running costs. NOI = effective gross income − operating expenses, and by appraisal convention NOI excludes the mortgage, the capex reserve, and income tax. Vacancy is taken off gross rent first to get effective (collected) rent, and property management is charged on that collected rent, not gross. The capex reserve is a real set-aside, so it is left out of NOI but subtracted in the investor cash-flow line.
What is cash-on-cash return?
Cash-on-cash = annual pre-tax cash flow ÷ total cash invested (down payment plus closing costs). It’s the yearly cash return on the money you actually put in, before financing paydown, appreciation, and taxes.
What is a good monthly cash flow?
There’s no universal number. Some investors want a per-door minimum, others accept thin cash flow for appreciation or debt paydown. What matters is that the number here is honest: realistic rent, realistic vacancy, and expenses from quotes rather than guesses. The conservative / expected / optimistic view shows how the deal moves if rent is a little softer or stronger.
Why does vacancy matter so much?
A vacant month costs the full rent but none of the expenses stop. Even 5–6% vacancy (roughly three weeks a year) shifts cash flow meaningfully on thin deals. Underwrite with a vacancy assumption you can defend, not zero.
