These words ALWAYS go through my mind, "if I get paid for a shoot, what if I mess up their pictures?"
Well, if it's portraits, you reshoot. If it's something else like an event - well - you work something out and/or refund the $$. People generally understand that stuff happens. (See my most recent blog entry about the things that went wrong on a recent paid shoot! http://forums.photographyreview.com/...howjournal&j=5) However, if you generally find that you don't screw things up when shooting for yourself, I think you'll find that you won't screw it up when being paid either. I'm not saying this to be cheeky, I'm trying to be encouraging. Utterly screwing up is a fear of mine, as well, every time I shoot for $$. If you really want to be a commercial photographer, though, I strongly encourage you to take a deep breath and go for it!