While I don't think it's realistic to say that anyone can be a pro, but I also think that all you need is average genetics for putting on muscle. The most difficult thing about becoming a pro (politics excluded) is contest prep., thats why you see so many guys try time and time again. When you are a walking pharmacy and there are so many variables besides just food and training it can be pretty fucking difficult. Thats why there are so many pre contest gurus out there that make good money doing what they do. And yes we have all seen the guys that use and still look like shit, but do any of us know what their training is like, their diet, did they have at least 2-3 years of natural lifting under their belt or did they start using as soon as they picked up a barbell. Just about anyone has the mental capacity to make an omlette but I guarantee you that there are morons out there that could manage to fuck it up.