Can they legally kick them out? If not, then there is a problem. But if they can legally kick them out and can legally engage in the sexual act with them (so ruling out cases where the other party is underage, intoxicated, ect.), aren't they just saying 'do this legal thing for me or I'll do this other legal thing that I think you won't like'.

My understanding is that you cannot just kick out someone who has been living their legally, so let's make it a legal action instead. "Start having sex with me or I'll start the eviction process." If that is rape, then should not "Start paying or I'll start the eviction process" would be theft?