Paying Off In 15 Years

As soon as you make an extra principal payment, you then owe less interest than was scheduled for the next month, because you are borrowing less money.If you have -- for example -- an eight percent mortgage, every hundred dollars extra you send in should save you eight dollars a year from then on.

I say "should" because it's important to check that the money is being properly credited toward principal, not just stashed into your escrow account.)

These days you'd be lucky to pick up four percent from an interest-bearing account.So if it's stashed there, the hundred dollars would earn four dollars a year, instead of saving you eight dollars on the mortgage.You'd be five dollars out at the end of every year.

I'm ignoring income tax consequences.The tax aspect isn't important enough to influence your decision.