How to calculate rental property cash flow
Cash flow = rent − vacancy − operating expenses − mortgage payment. Operating expenses include property tax, insurance, HOA, maintenance, capital expenditure reserves (roof, HVAC, appliances), property management and any utilities you pay. Net operating income (NOI) is income minus operating expenses before the mortgage.
Key metrics explained
- Cash-on-cash return = annual cash flow ÷ total cash invested (down payment + closing costs + rehab).
- Cap rate = annual NOI ÷ purchase price. It ignores financing, so it compares properties fairly.
- DSCR (debt service coverage ratio) = NOI ÷ mortgage payment. Many DSCR lenders want 1.0–1.25 or higher.
- 1% rule: monthly rent ≥ 1% of price is a quick screen, not a verdict.
Common mistakes
Forgetting vacancy and CapEx, using the seller's rent numbers, and ignoring rising insurance and taxes. Use the projection table to stress-test growth assumptions.