Most of the common morphs you won't get a lot of money for. But if you were to breed some one the rarer morphs you could make a heck of a lot of cash with.
I'd ask around at some of the local reptile stores to see how much they will give you for them before you start breeding them. The stores near me give me $25-$40 depending on how they look.
Leopard Geckos were the first lizard species I ever bred. It's really not too difficult to do and most will breed without any effort on your part.
I've got 20 eggs incubating right now and here's a pair that hatched last week for me. Their father is a Tangarine Het Bell Albino and their mother is a High Yellow. I can't wait to see what they look like in a few months.