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Finance & LoansGenerated accuracy model review: 2026-05-06
Rent vs. Buy accuracy and testing
This page documents how Calwarden builds trust for this calculator: source notes, regression-style default tests, limitations, assumptions, unit handling, rounding, and visible change history.
Formula source
- The calculator sums up all unrecoverable costs for both scenarios: **Buying Costs**: Mortgage Interest + Property Tax + Maintenance + Buying/Selling Fees - Appreciation Gains. **Renting Costs**: Total Rent Paid (adjusted for annual increases) - Investment Gains from saving the down payment difference.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Home Price: $400,000
- Monthly Rent: $2,500
- Time Horizon: 7 Years
- Home Appreciation: 3%
- Mortgage Rate: 6.5%
Expected outputs
- Cheaper Option: Buying
- Net Cost Buying: $132,799.29
- Total Cost Renting: $229,873.87
Known limitations
- Assumes standard deduction for taxes (does not calculate mortgage interest deduction benefits, which vary by individual).
Assumptions
- Buying assumes a 20% down payment, a 30-year mortgage, and simplified maintenance and property-tax rates.
- Rent grows at a fixed annual rate and buying costs include a simplified selling-cost estimate.
- This is a directional financial comparison, not a full personal housing model.
Unit handling
- Home Price accepts values in $.
- Monthly Rent accepts values in $.
- Time Horizon accepts values in Years.
- Home Appreciation accepts values in %.
- Mortgage Rate accepts values in %.
- Net Cost Buying is displayed as currency.
- Total Cost Renting is displayed as currency.
Rounding rules
- Number displays use up to 2 decimal places in the calculator UI.
- Currency outputs are displayed with standard US dollar formatting.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current rent-vs-buy-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for Rent vs. Buy.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.