1. Build the true acquisition basis
Start with purchase price, buyer closing costs, immediate repairs, permits when applicable, financing costs and a repair contingency. If the property needs work before it can produce rent, include the carrying period before stabilization.
For a value-add deal, separate repairs required to make the property rentable from optional improvements intended to increase rent or resale value.
2. Underwrite rent conservatively
Use recent, genuinely comparable rentals rather than the highest advertised rent you can find. Adjust for property type, size, bedroom count, condition, parking, utilities, furnishing and exact micromarket.
Then model vacancy and collection loss instead of assuming twelve perfect months every year.
3. Include the complete operating expense load
Typical underwriting may include property taxes, insurance, HOA or CDD, management, repairs and maintenance, landscaping or pool service, utilities paid by the owner, leasing costs, reserves and other property-specific expenses.
IRS Publication 527 identifies common rental expenses for tax reporting, but tax treatment and depreciation should be confirmed with a qualified tax professional. Investment underwriting and tax accounting are related but not the same calculation.
4. Use NOI, cap rate, cash flow and cash-on-cash for different questions
NOI is operating income after vacancy and operating expenses, before financing and income taxes. Cap rate compares NOI with property value or acquisition basis. Cash flow includes debt service. Cash-on-cash compares annual pre-tax cash flow with the cash actually invested.
- NOI = effective rental income − operating expenses.
- Cap rate = NOI ÷ property value or acquisition basis.
- Cash flow = NOI − debt service and other financing-period cash items.
- Cash-on-cash return = annual pre-tax cash flow ÷ cash invested.
5. Stress-test the deal before calling it an opportunity
Run at least a base case, downside case and upside case. In the downside case, test lower rent, more vacancy, higher insurance, higher repairs and a larger capital reserve.
For Florida property, verify flood mapping and obtain real insurance indications early. FEMA provides the official NFIP flood map source, but a flood zone alone does not determine the final premium or underwriting decision.
Common questions
Is cap rate the same as cash-on-cash return?
No. Cap rate measures property-level operating performance before financing. Cash-on-cash return measures pre-tax cash flow relative to the cash you invested.
Should mortgage principal be included in NOI?
No. NOI is calculated before debt service. Financing belongs in cash-flow and cash-on-cash analysis.
Can a property with positive cash flow still be a weak investment?
Yes. Deferred repairs, insurance risk, weak reserves, unrealistic rent assumptions or poor exit liquidity can make apparently positive cash flow misleading.