In all honesty I think it's going to be difficult to make money hatching and selling chicks. I'm not saying don't try, but once you factor in the cost of buying your breeders, the time it takes them to reach maturity and the feed they eat until that time, the expense of building the housing if it is not already built, and all the other costs involved in running a coop you might find it difficult to turn a profit.
I kept records of my flock this year and my flock pays about half of it's expenses. I also raise show birds so I can ask a higher price for the show quality birds. Mind you, I could probably do a bit better if I only sold chicks and didn't keep them until they were older.
If I were going to try it I would research heritage breeds as they are experiencing a surge in popularity. I find colorful birds also sell better than solid colored birds, and silkies always seem to be popular.
Good luck and let us know how it goes!
Urban Coyote