I make a few bucks breeding, they support themselves with a few bucks left over. Nothing to quit the day job over, I'd make more money working a couple of Saturdays a month.
I sell around 200 angels on a good month, zero on a slow month, it's all supply & demand. With 16 tanks I could put out 300-400 monthly if the demand was there & I maxxed out all my tanks. I average 75 cents to $1.50 per angel, but you have to subtract electric, food, water, & initial startup costs. Take out for maintenance supplies, and there isn't much of a profit margin.
If you want to try it, by all means go for it. I know quite a few retired guys on a fixed income who breed to make a few extra dollars. There are also larger breeders online who make money supplying fish. One of the lfs owner in my area started as a kid breeding in his parents basement using anything that would hold water for a tank, sealed up refrigerator liners from the junkyard was one of his favorites. The more you can cut overhead, the more profit you will see.
Always provide a superior product, the lfs buying from you has to beat the larger corporate owned chains, and better fish is one of the ways they do it.