CalcStack — free, instant, no signup. The interactive calculator loads automatically.
A $300k rental at 7% with $2,400 rent loses $152/month — the tool that tells you before the closing does.
At 2026 mortgage rates, most listed rentals are cash-flow negative, and the ones that aren't fail the moment you price management, vacancy, and reserves honestly. This calculator runs the lender-grade model: gross rent minus vacancy gives effective income; taxes, insurance, management, maintenance, and CapEx reserves give NOI; debt service gives the verdict. A $300,000 purchase with $2,400 rent at 7% runs −$152 a month with a 0.90 DSCR — a deal no DSCR lender would touch, priced honestly. The levers are price, rate, and rent, and the tool shows what each is worth. Cross-checks included: the 1% rule, the 50% rule, and cash-on-cash on your real cash in.
Investors use it before offering: the lender-grade model prices vacancy, management, and CapEx honestly, so a $300k/$2,400-rent deal at 7% shows its real face — −$152/mo, 0.90 DSCR — instead of the seller's proforma fiction.
The floor most investors quote is 8–10% cash-on-cash with all reserves priced in — below that, a REIT or index fund pays similar returns with zero 2 a.m. phone calls. But the real answer depends on what else the deal pays: principal paydown (~1.2% of the loan in year one, growing), depreciation shelter (a $300k rental shelters ~$9,400 of income over 27.5 years), and appreciation. A deal at 4% CoC in a genuinely appreciating market can beat a 10% CoC deal in a flat one on total return — but only cash flow keeps you solvent through the flat years. The non-negotiable: negative cash flow means YOU are the subsidy, and "appreciation will cover it" is speculation, not investing.
Debt Service Coverage Ratio = NOI ÷ annual debt service — the property's ability to pay its own mortgage. DSCR lenders (the main channel for investor loans in 2026) want 1.20–1.25 minimum: the property clears its payment with 20–25% headroom. Below 1.0 the property literally cannot pay its own mortgage — you feed it monthly. DSCR loans price on the ratio: expect rate hits of 0.5–1.5 points as DSCR falls from 1.25 toward 0.75, and LTV caps tighten too. The practical use: solve backwards — at a given rate and price, DSCR ≥ 1.2 tells you the minimum rent the deal needs. If market rent isn't there, the price has to come down or the deal doesn't exist.
Because proformas are sales documents. The standard omissions: no vacancy (use 5–8%), no management ("I'll self-manage" — then your labor is the expense, 8–10% is the honest number either way), no CapEx reserve (roofs and HVACs are when, not if — 5% minimum), and "market rent" that's $200 above market. This tool's 50% rule cross-check exists for exactly this: if your itemized expenses come in far under half of gross rent, you've underpriced something. When itemized and 50%-rule NOIs disagree, trust the worse one. And verify rent from actual leased comps — Rentometer or signed leases nearby — never from the listing.