If your final goal is to sell them then you have two options. For a quick turnover you should try mbuna or other small fish, which have vivid colors at any age. The pitfall here is the price you will get. Most people keep mbuna who happen to be very prolific too, so the price you will get is very low. On the other hand, you can sell them easily at 4-5 months.
Haps are exactly the opposite.
Still, females don t look that attractive and some hobbyists prefer a male only aquarium. So, it is up to you really. If you have plenty of tanks this will not be a problem, since you can successfully raise all the fry you can get. However, in most cases, the tank space is limited so, in order to raise the fry of one species you must first empty the tank from the previous fry. This is really a headache.