How we calculate every number you see.

We start with the monthly rent you enter. If you indicate other income (parking, laundry, storage, pet rent), we add it. We do not assume any rent growth in year one — what you enter is what we model.

gross_income = base_rent + other_income

Every operating cost is subtracted line by line. If you leave a field blank we substitute the conservative defaults below to prevent overly optimistic results:

• Property taxes — entered amount; no default.
• Insurance — entered amount; no default.
• Vacancy reserve — default 7% of gross rent.
• Maintenance reserve — default 8% of gross rent.
• Property management — default 8% of gross rent (set to 0 if you self-manage).
• HOA / body-corporate fees — entered amount.
• Utilities you cover — entered amount.

opex = taxes + insurance + vacancy + maintenance + management + hoa + utilities

NOI is what the property earns before financing. It deliberately excludes mortgage payments so it can compare properties on equal footing.

NOI_annual = (gross_income − opex) × 12

The capitalization rate measures unlevered return on the property's purchase price.

cap_rate = NOI_annual / purchase_price

We treat 5–8% as a healthy band for residential rentals and flag anything below 4% as "appreciation-dependent".

Standard amortising mortgage formula, monthly compounding:

P = L × (r × (1+r)^n) / ((1+r)^n − 1)
where L = loan amount, r = monthly rate, n = months

cash_flow = gross_income − opex − mortgage_payment

This is the number that hits your bank account each month after every bill is paid.

Annual pre-tax cash flow divided by the cash you actually invested (down payment + closing costs + initial repairs):

coc = (cash_flow × 12) / cash_invested

dscr = NOI_annual / (mortgage_payment × 12)

Most lenders look for ≥ 1.20. We flag anything below 1.10 as high risk.

Our composite score weights five factors:

• Cash flow margin (30%)
• Cash-on-cash return (25%)
• Cap rate (20%)
• DSCR / safety margin (15%)
• Stress-test resilience (10%)

Each factor is normalised against industry-standard thresholds, clamped to 0–100, then combined. Verdict bands: 75+ Good · 50–74 Risky · < 50 Bad.

We re-run the entire calculation under three downside scenarios and report which ones still produce positive cash flow:

• Rent drops 10%
• Vacancy doubles
• Interest rate rises 2 percentage points

• We don't model taxes, depreciation, or your personal income tax bracket.
• We don't model appreciation in the headline numbers — that's a deliberate conservatism choice.
• Currency is purely cosmetic; the math works for any currency.
• Local landlord-tenant law and tax rules are not encoded — always consult a local professional.