Massages and rub-downs are common therapies. You just don't want to cross the line into sexual conduct for money. It takes two to tango; so don't let things get out of control, if propositioned. You might get stung.
Prostitution is illegal just about everywhere except a few counties in Nevada. If you are worried about the legality decline the extra services offered or better yet, get the rub down from a licensed massage therapist instead of the Tokyo Spa or wherever.