Mortgager
A rent-or-buy calculator for the Dutch housing market, with the full monthly mortgage schedule and the month buying starts to pay off.
Mortgager takes a property price, loan term, interest rate, rent and expected market growth, plus upfront costs like overbidding, fix-ups and agent fees. It then builds the month-by-month schedule of an annuity mortgage. From that it finds three break-even points: when buying beats renting, when selling would turn a profit, and when renting the property out would pay off the debt.
It accounts for Dutch property transfer tax, including the first-home exemption for buyers under 35.
The calculator is written in Python. The hosted version runs that same Python code in your browser with Pyodide, so there is no server behind it.