Sometimes I have been greeted by a door opening into a darkened area of some kind (with the provider behind the door and not visible) and told to follow the provider to their "studio" (not in those words, maybe) but, due to the bright outside, and then entering a darkened area, your eyes can't adjust enough to see much of anything. By the time you can see what the provider looks like, its too late to simply turn around and leave. But, even in this situation if there were obviously major discrepancies to the negative side, I wouldn't have a problem saying "I don't think it will work", or similar, and leaving. I think the situation described is much more of a problem for an escort visit, however, rather than a masseur.