Rental Property Calculator

Positive monthly cash flow after all expenses is the non-negotiable foundation of sustainable rental investing. Appreciation is a bonus — it can and does stop — not a strategy you should depend on to service a negative-cash-flow property. A deal that loses $300 per month requires you to fund those losses indefinitely, which caps your ability to scale and exposes you to serious risk if rents drop or a major repair hits simultaneously. To calculate true cash flow, deduct not just the mortgage but also vacancy loss, property management, property taxes, insurance, maintenance, capital expenditure reserves, and any HOA fees. For a single-family rental, realistic vacancy runs 5–8% of gross rent and maintenance plus CapEx reserves another 10–15%. Many first-time investors undercount these expenses and discover their "profitable" deal actually loses money. Run your numbers through this calculator with conservative assumptions — if the deal still works at 10% vacancy and $150/month in reserves, it is likely resilient enough to hold. If it only pencils out at 100% occupancy with no repairs, pass.

Budget 5–10% of gross rent for vacancy, 5–10% for repairs and maintenance, and 8–10% for property management even if you plan to self-manage initially, because your time has real value and circumstances change. Also reserve 5–8% for capital expenditures — the large irregular costs like roof replacement, HVAC, water heater, and appliances that can easily run $5,000–$20,000 in a single year. Underestimating expenses is by far the most common mistake new investors make, and it turns paper-profitable deals into cash-flow negative headaches. Use the 50% Rule as a quick sanity check: if your total operating expenses (excluding mortgage) look likely to exceed 50% of gross rent, scrutinize each line item carefully. The 50% figure is a rule of thumb, not a guarantee, but properties where expenses run well above 50% — because of age, deferred maintenance, or high taxes — often produce disappointing returns even in appreciating markets. This calculator shows your exact expense ratio so you can compare it against market benchmarks.

With 25% down on a $300,000 property that appreciates 3% annually, your $75,000 equity stake grows by $9,000 in year one — a 12% return on invested capital purely from appreciation, before factoring in cash flow. That amplification is the power of real estate leverage. But leverage cuts both ways: in a 10% price decline, you lose $30,000 on a $75,000 investment — a 40% loss. This is why maintaining adequate cash reserves (aim for 6+ months of total housing expenses per property) is essential, especially early in ownership when unexpected costs are most likely. The Debt Service Coverage Ratio (DSCR) is your early-warning system — if NOI divided by annual debt service falls below 1.25, the property's income barely covers its debt obligations, leaving almost no margin for vacancies or repairs. Lenders typically require DSCR of at least 1.25x to approve financing, and you should use the same threshold internally even if you already own the property free and clear.

DSCR (Debt Service Coverage Ratio) is a metric that matters even when a property is technically cash-flow positive. A property earning $100/month in cash flow after all expenses sounds fine, but if NOI is only 1.05x the annual debt service, any rent interruption or unexpected expense immediately turns it negative. More importantly, DSCR below 1.25x will prevent you from refinancing the property in the future — a critical obstacle if you plan to execute a BRRRR strategy or need to pull equity for the next acquisition. Track DSCR alongside cash flow every time you model a rental deal. A DSCR of 1.35x or higher gives you room to absorb rising insurance costs, a rent-free month during tenant turnover, or an unexpected repair without defaulting on obligations. As a portfolio investor, you should also consider your aggregate DSCR across all properties — one strong asset can mask several weak ones, creating hidden portfolio risk that only becomes apparent during a broad economic downturn or credit tightening event.