No. You are buying services, not the body. At least, that's the underlying principle. Whether or not the johns understand that is something of a crap shoot, as I understand it. (I live in a state where a judge has ruled that prostitutes cannot be raped; there is very little I can say about that that falls anywhere near the realm of civility.)
Depends on the terms. A john should not presume that just because he has bought "sex" he can do whatever he likes. Nor should a prostitute presume that the john understands that. Specific terms should be set.
I'm going to go with no. If you are the pimp, facilitating the sale, the answer is yes.
im sure this came up in that thread on porn stars as well, the courts couldnt and wouldnt impose a remidy (at least here) which required someone to have sex (i wonder what would happen to an impotent prostitute, they would be incapable of forfiling the contract which would make it invalid *shrug*) but they might well require compensation to be paid (especially if it GOT to the courts) and civil penelties for theft might well applie if they took money and refused the service