When you talk about 10 inch plus fish, you're selling to a HIGHLY specialized market, even if you sell nationally on the Internet. You'll also need a few tanks to do it. And if you're breeding SA/CA cichlids, you have to grow them out to some size so you can get a good price for them.
I think if you had LOTS of space, lots of tanks, or a couple pools/ponds outside where it doesn't get cold, you'd do great if you bred several different species. But, to just do it in your house would be tough.
That being said....if you started with good fish from a highly reputable source, I gotta believe you could make some money on Herichthys Labridens -- Yellow Labs. Those things are SO expensive. I'd buy 10 or 20 off you if you were posting pics, and breeding videos, and posting on forums about your WC Yellow Labs you got from Rapps/CoA/whoever.
Any of those hard to find Nosferatu, Herichthys species would be awesome.