Car Affordability Simulator
Budget your vehicle purchase price under the golden 20/4/10 rule. Run side-by-side financing loan amortizations vs lease terms instantly.
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Affordability Profile📊 Affordability Dashboard
Budget SafeAuto Finance Rules: The 20/4/10 Rule and Lease vs. Buy
📋 What is the 20/4/10 Rule of Car Buying?
The 20/4/10 rule is a conservative budgeting rule designed to keep auto expenses in check. It states that you should: 1. Put down at least 20% down payment to avoid negative equity. 2. Finance the vehicle for no more than 4 years (48 months) to limit interest fees. 3. Spend no more than 10% of your gross monthly income on total transportation costs (loan payment, insurance, gas, and charging).
🔑 Buying vs. Leasing: The Math
Buying (Financing) builds long-term equity. Once the loan is paid, you own the asset outright. However, loan payments are higher because you pay down the entire vehicle value + interest.
Leasing results in lower monthly payments because you only finance the expected depreciation of the vehicle over the term (e.g. 3 years), plus a money factor rent charge. The downside is that you must return the car or buy it out at the end, having built zero equity.
Avoid the "Monthly Payment" Trap
Car dealers often stretch loan terms (e.g. to 72 or 84 months) to make a expensive car fit a lower monthly target. Under the 20/4/10 rule, this is avoided because loan lengths are strictly limited to 48 months. Shorter terms force you to target cars that match your actual income, saving you thousands in interest fees.