What is the best short term/large gain investment for approx. $25,000.00?

Answer 1

Boy, you're going to have to get educated on this, or you're likely to lose your money.

However, if you know what you're doing, you could buy houses, clean them up a little, and flip them. BUT, you really, really, really want to know what you're doing before you go into this, as the saying is true: a fool and his money are soon parted.