There is nothing. Sex is just sex. Lies are what kill. My wife set the rules for my play and I follow them to the letter. To do less would be cheating and that would be wrong. My wife now plays by the rules I set forth. She is no longer cheating as long as she sticks by those rules. And what is wrong for performing a service for money as long as you are not breaking a trust you made? In my mind nothing, the sin lies with the cheater. If you are honest and open and your SO is OK with it what is wrong with playing on ether side of the envelope? In my mind nothing. If you are single what is wrong with paying for it? Again nothing in my mind. If you are lying and hiding ether side from those you have made a commitment to is it wrong? You better believe it. The lies and omissions and the removal of choice about what risks to take make it so.