# Ledgerly Rent vs Buy Calculator

> Rent or buy? Break-even year, net worth over time, scenarios and a sensitivity table. Simulates buying and renting month by month: mortgage schedule, buying and selling costs, property tax, maintenance, insurance, rent increases and the return the renter earns by investing the down payment and every monthly difference. Shows the break-even year, net worth on both sides, home-price scenarios and a sensitivity table. Part of Ledgerly’s Reality Check.

Part of usefulweb.app (https://usefulweb.app/). Part of [Ledgerly](https://ledgerly.usefulweb.app/) (ownerApp: ledgerly). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://ledgerlyrentvsbuy.usefulweb.app/ (interactive tool at https://ledgerlyrentvsbuy.usefulweb.app/tool)
- JSON API: POST https://ledgerlyrentvsbuy.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://ledgerlyrentvsbuy.usefulweb.app/api/v1/tool)
- OpenAPI: https://ledgerlyrentvsbuy.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://ledgerlyrentvsbuy.usefulweb.app/mcp - tool `ledgerly_rent_vs_buy`

## Inputs
- currency (text): Currency - ISO code used for the labels, e.g. EUR, USD, CHF.
- homePrice (number): Purchase price of the home
- downPaymentPercent (number): Down payment (% of the price)
- buyingCostsPercent (number): Buying costs (% of the price) - Transfer tax, notary, land registry and agent fee, paid in cash on top of the down payment.
- mortgageRatePercent (number): Mortgage interest rate (% per year)
- mortgageYears (integer): Mortgage term (years)
- propertyTaxPercent (number): Property tax (% of the home value per year)
- maintenancePercent (number): Maintenance (% of the home value per year)
- ownerInsurancePerYear (number): Home insurance per year
- ownerFeesPerMonth (number): Other owner costs per month - For example service charges or a home-owners association fee that is not maintenance.
- appreciationPercent (number): Home price growth (% per year)
- sellingCostsPercent (number): Selling costs at the end (% of the value)
- saleGainTaxPercent (number): Tax on the gain when selling (%) - Often 0 for an owner-occupied home; enter your local rate if a gain is taxed.
- rentPerMonth (number): Rent per month (comparable home)
- rentIncreasePercent (number): Rent increase (% per year)
- renterInsurancePerYear (number): Renter’s insurance per year
- costIncreasePercent (number): Increase of insurance and fees (% per year)
- investmentReturnPercent (number): Return on invested savings (% per year) - The opportunity cost: what the down payment and every monthly difference would earn if invested instead.
- investmentTaxPercent (number): Tax on investment gains (%)
- horizonYears (integer): Years to compare
- scenarioStepPercent (number): Scenario step for home price growth (percentage points)

## Method
- The mortgage is a monthly annuity built with the same schedule engine as the Loan Amortization Calculator (integer cents, interest rounded per month).
- Buying needs the down payment plus buying costs in cash; the renter invests exactly that amount instead. Each month the side with the lower costs invests the difference, so both sides spend the same money.
- Owner costs: mortgage payment, property tax and maintenance (percent of the home value at the start of each year), insurance and other fees (growing with the cost increase). Renter costs: rent (growing with the rent increase) and renter’s insurance.
- Net worth in year N: buyer = home value − selling costs − tax on the sale gain − remaining mortgage + invested surplus after tax; renter = invested savings after tax on the gains. The break-even year is the first year buying is ahead; “not stable” means it falls behind again later.
- Scenarios move the home price growth by ± the scenario step; the sensitivity table varies price growth (rows, ±2 steps) and the investment return (columns, ±2 percentage points).

## Limits
- A model, not advice: house prices, rents and returns are uncertain, and local taxes and subsidies differ. Change the inputs to match your offer and check the sensitivity table before deciding.