Before breeding to sell reverse engineer it. Go to local shops, ask around local clubs. What sells well here might not sell well at all 100 miles away, I've seen that time & time again. It's very local, and can change rather quickly depending on breeders flooding your local area with that species, or a larger breeder dropping out.
Find the species folks are looking for, pick the one that fits what you can handle as far as space, water, and experience, then have at it. As far as your water & pH, hardness has not been mentioned. This is often more important than pH when breeding, and is another water parameter which must be taken into account.
Plan for more tank space for growout & holding, half the shops that say they will buy them will back out when you have fish ready. Look for deals on used tanks, empty tanks cost nothing to run, you will never find a deal on one if you suddenly need space. Run spare filters for the empties, by cloning you will have an instantly cycled tank.
Consider the diet of adults being conditioned for spawning as well as actively breeding. Also take into account food for newly hatched fry, this most often means setting up & running a baby brine shrimp hatchery.