No tax. Rental income is taxable, treatment varies by your total income, residency status and whether the property is loan-financed, and the standard deduction and interest treatment materially change the answer. Modelling that here would produce a confident number that is wrong for most users. Take it to a chartered accountant.
No leverage. If the purchase is financed, cash-on-cash return and net yield diverge sharply and interest cost dominates the answer. This calculator models an unlevered purchase.
No capital appreciation. Yield is the income question only. Total return is yield plus capital movement, and the second term is where most of the disagreement in this market lives.
No rent or cost escalation. This is a single-year snapshot at today's inputs, not a discounted cash flow. Society dues and property tax rise; rents rise in steps at renewal, not smoothly.
Nothing is stored. The calculation runs entirely in your browser. Nothing is sent anywhere unless you press the button to message the scenario to me, which composes a WhatsApp message you can read and edit before sending.