Its a flooded market. You'll get nowhere. Every little budding webmaster tries to make money with this method. Look for something harder, and less crowded than that, and carve yourself an easier niche. If you do something related, then you could eventually branch out and do this. However if its just about the money. Your effort would be a bloody finger, surviving in thousands of pirahanna fish. You'll get chewed up and spat out before you ever get any clients, and if you do, you have such little idea about the real complexity of good backlink services, you'll just spoil the soup, and end up with negative feedback, and getting banned.