Going for the most expensive fish won't always get you profit in the long run, get a fish that your LFS will be able to sell easily and is always in demand. go to your LFS and talk to them about what fish are in demand and are difficult to come by.
That would be a good start. Get your fish from an experienced breeder and become friends with the owners of the LFS that will help you a lot when it comes to selling time. finally when you have a list of fishes that you may want to breed find out how easily they breed and how often they breed and if they need any special requirements.