At 6%, interest ≈ the house itself

On a 30-year mortgage above ~5.5%, total interest roughly equals — then exceeds — the amount borrowed.

Why it works

At 6.5% over 30 years you repay about 2.3× the principal. Extra principal payments early on attack exactly this.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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