Mortgage Prelude 2.6.1
This mortgage calculator computes such items as your monthly payment, amortization schedules, interest, etc; but it is so much more.
You can actually find out how much of a mortgage you are qualified to get! It uses the guidelines set forth by the Federal National Mortgage Association (a.k.a. Fannie Mae) in its computations. This is a very important concept because they are the same rules most lending institutions use.