It boggles the mind how often people ask this sort of thing. As if never asked before.
Number One: Where are you talking about? Criminal law varies from one place to another. In Canada, criminal law is made by the Parliament in Ottawa for the whole country. Same everywhere, up here. In the US, each state has their own criminal law. In Rhode Island, prostitution's not criminal, in some other states it is, some places john's commit a crime by buying, some places it's all misdemeanour stuff.
Number Two: If you're talking the T in TERB, it's the same as anywhere in MapleLand and it's been answered ad nauseam in each of the Forums. Search button, top of page, and read some past pages before posting a trite question. Try: "legalities" or "bawdyhouse". Or Google.
Number Three: Sex for money i.e. prostitution is legal in Canada.
Number Four: Using force or undue influence, involving minors in any way, and other things you wouldn't dream of—like doing it in public—are crimes, so is receiving a cut of the proceeds. The criminal bits you do want to watch out for: "Communicating for the purpose" in a public place: Don't do any deals with hookers on the street. Being 'found-in' a 'bawdy-house', which is a place 'customarily used for prostitution' i.e. a brothel, bordello, whorehouse, MP (perhaps), SC (maybe), Incall, hotsheet hotel, or your office (if it gets to be regular w/ you and the boys 'n' girls). And yes, 'found-in' means exactly what it says, doesn't matter your pants stayed on and your money's all still there.
Number Five: If you're asking from NY or someplace other than TERBville, you really should know more about your local laws than some strangers somewhere on the interweeb.
And this is true everywhere: Lawyers didn't get their rates up to multi hundreds an hour because the answers were easy straightforward and simple.