Rental Property ROI and Cash Flow Calculator

A rental property can look cheap on gross yield and still lose cash after the mortgage, vacancy, and repairs. Cap rate isolates operations from financing: net operating income divided by purchase price. Cash flow then subtracts debt service. The rental property calculator also reports a first-year return that adds assumed appreciation to cash flow and divides by the down payment, which is more aggressive than textbook cash-on-cash (cash flow / cash invested). Effective rental income = monthly rent × 12 × (1 − vacancy rate). Operating expenses = annual taxes + insurance + maintenance + (monthly rent × 12 × management fee). NOI = effective income − operating expenses. The mortgage is the standard amortizing payment on price − down payment. Annual cash flow = NOI − 12 × monthly mortgage. Cap rate = NOI / purchase price. Year-1 return including appreciation = (annual cash flow + purchase price × appreciation rate) / down payment. Investors use cap rate to compare unlevered deals in the same market and cash flow to see whether the loan is serviceable each year. A 10% cap with negative cash flow usually means the debt is too heavy, not that the building earns nothing. Raising vacancy or adding professional management is the fastest way to stress-test a listing that assumed 0% empty and self-management with no capex. The model is a first-year snapshot. It omits closing costs, capital expenditures beyond the maintenance line, income tax, depreciation, and principal paydown as a separate equity benefit. Appreciation is an assumption, not a coupon. A negative cash flow can still show a high year-1 return if appreciation is large; read cash flow first. Use a rent roll, tax bill, and lender quote for a live offer, and have an accountant review returns before you buy or bid in an auction.