I agree with... Buy fish you like.. hope they breed, and you can sell off some babies to offset your feed bill.... unless your are setting up a massive system or tanks ect your not going to make money "small time breeders" are all hobbyists for a reason. they break even if lucky. may as well do it with fish you enjoy haveing around. Kevin's point about the rays is imo being very generouse... rays are also more delicate and require a certain level of dedication, and overall experiance with fish ( not sure where the OP falls in this bracket) The market is also fairly small, and if you don't know what your doing you can get into trouble easily with shipping/ect.
And i think the point that most if not everyone here has liekly thought of doign this an how many actually are either breaking even or comign ahead shows how impractical it is... I still have my goals of breeding certain species, and no one will ever dissuade me otherwise, but i've learned not to expect to make money on the endevor.