A porn star, no. I would hate to take the sensuality out of sexual intercourse. Also, watching a spliced together three minute montage of a cum shot doesn't give a person realistic expectations. Compound that with my physical attributes and I don't think the camera would be nice to me.
A prostitute, however, is something I've fantasized about. The only problem, like others have stated, is I don't want to contract a disease from some sick bastard. If there were no risk of disease, shame, harm, reputational damage, or splitting the money with a pimp... then maybe, but refer to 'physical attributes' above.
I would love to be a slave or sub, but I'm not sure how to approach the misses about being a master or dom. This would relieve me of all responsibilities and for me, I think that's the magic key. If I could just say, "I had no choice. I had to take a (pegging, gang bang, dog, horse, etc) because I'm a good sub."