Underwrite
Rental property cash flow calculator
Positive vibes on a listing photo are not cash flow. Rent comes in; vacancy, taxes, insurance, repairs, management, and the mortgage go out. Enter the stack; see monthly and annual cash flow before you fall in love with the kitchen.
Assumptions
Returns stack
- NOI (annual)
- —
- Monthly cash flow
- —
- Annual cash flow
- —
When to use
First-pass underwriting, stress-testing a higher vacancy, or deciding whether a “small” repair budget is lying.
When not to
Don’t call rent-covers-the-PI “cash flow positive” if taxes, insurance, and repairs still eat the rest. Principal paydown is equity, not cash in the checking account here.
Assumptions: Cash flow = NOI − debt service. CapEx reserves should be modeled or you’re inflating the result.
Worked examples
Input
Rent $2,200 / mo Vacancy 5% OpEx $700 / mo Debt $1,100
Output
Cash flow ≈ $290 / mo
A thin but positive month — check CapEx and vacancy stress next.
Input
Same rents OpEx $950 / mo
Output
Cash flow ≈ $40 / mo
Expense assumptions can erase the deal.
Common traps
- “I self-manage so OpEx is $0” is how people underwrite hobbies.
- Principal paydown is equity build — usually not counted as cash flow here.
- Seasonal STR income needs occupancy, not fantasy ADR × 365.