The keys to raising fish for profit are to raise fish that are high demand at young ages, moderately rare and not commonly found in lfs, and easily bred and raised. To reduce your overhead costs there are lots of club swaps and auctions found throughout the country and many may be close to driving distance for you. Table rents are cheap and you don't have to worry about shipping, or problems with payment. You may be able to sell fish only 3-4 times a year but when you do the cost is low and the exposure to customers is high. If you figure that it takes that long at least to raise a batch of fry you should have sellable fish to raise at any time.
Some species that I have worked with in the past and do well are BN plecos, Fancy guppies, Geophagus cichlids (just about any species but the larger and rarer ones do best), Endler's livebearers, Metriaclima demasoni, any kind of shrimp, and just about any Malawi Peacock or Utaka (sold in trios is best).
Fish to avoid are Malawi mbuna (with a few exceptions like Demasoni and Saulosi) as they are commonly available and easily bred, Angelfish (Market is saturated with breeders and the price is low), and Convicts (ultra saturated fish are hard to sell at any price).
Zebra plecos are an interesting conundrum. They don't spawn until they are about 3 years old, they only produce about 8-10 fry at a spawning, and are a year of growth to reach a sellable size. Wholesale price is about $150 a fish for a 1 year old fish and you won't get much more than that at swaps or auctions. They are fascinating to work with and it seems like you are getting a big payday when you sell them, but when you figure in all the money in food, energy, and time you put into them for the last 2-3 years it's really not much unless you are working with several pairs and get some kind of economy of scale. That's why this fish has been perennially high priced. They just can't be produced cheaply.
Good Luck,
Andy
PS. the 2012 ACA convention is coming up in about 2 weeks in Indianapolis and you should take the trip out to see how swaps and auctions (the auction is on Sunday) are done. You could find some new fish to work with and may be able to sell your angels in the auction.