Not gonna make any money unless you breed one of the more expensive species like Discus, Festae, EBJD etc, and even then you might not make much. People won't pay unless you can prove the quality of your stock, you can't just breed Petsmart mutts and then try to sell the fry. A baby festae from a high quality wild caught pair can be sold for $7 or 8 a piece at 1", but when you add the time, housing, food, maintenance, the cost of the parents (WC pair go for $300 and up. Some people want $300 for a single adult fish) and all the work you have to do in order to sell, pack and ship all of em, well... you get the idea. Then there are all the risks of breeding expensive fish (male killing the female, pair eating the fry, fish dying during shipments, etc, etc).
Then there's the competition. At the moment Festae are being bred by like 50 people on MFK alone, and Discus well... there's a whole industry dedicated to that. Basically there's no $ business in breeding Cichlids unless you plan to do it on a big scale (i.e. a fish farm or a small fish store).
Convicts are worthless as are most other common species JD, GT, Oscar, etc. They're so readily available that people don't even consider paying for shipping to get em for free.
But I'm talking about a decent amount of money here. If you just meant $50 bucks every now and then to buy cigarettes, there's a lot of species u can try. Just look for those with high demand.