Settlement Day !

[Flyinfool]

In the beginning the amount going to principle is tiny. But every time you can add the principle amount to the payment it knocks one month off the back end of the loan. As the years go by your income generally rises so it is easier to keep up with doubling the principle every month. You are also effectively banking the amount that was going to interest each month that you doubled the principal payment. So in the beginning you are adding a lot every month to the equity in the house.