Depending on the coral I often give frags or more common things away to others just starting out in the hobby as this is how I got started. If its something that is in demand I may trade it to the LFS for something else or auction or trade it at a local reef club meeting.
Given the right conditions, water parameters, lighting, flow and space some corals grow quite fast while others are very slow, maybe only a few inches a year.
I would not plan on making money off the hobby, thats pretty rare. I trade and barter for the corals I like, many are not high demand big names but they have a color or shape that appeals to me and compliments the other corals in my systems. I have never gone in for the high dollar stuff as usually in a year or so the bottom falls out and the prices come down where I can afford them.