It's not "legally controversial," it's against the law in nearly all US states, normally a misdemeanor. But I don't think most states would consider buying and selling of sex on Rentmen as a high priority for enforcement - the focus is on trafficking and street prostitution. Also, in the event that somebody wanted to use Rentmen for law enforcement purposes, a disclaimer that money is for time only is not going to be much help since there presumably would be ample evidence to the contrary.