i dont know if there would be much profit in it. but crayfish can be very easy to breed as long as they don't kill each other. check this out for more info http://www.bluecrayfish.com/reproduction.htm
Really depends on the species of crayfish. Do you know what species they are? If no post a pic and we will identify it for you. Usually breeding is simple, contrary to popular opinion, temperature and water hardness will trigger breeding.