I went down the criminal code rabbit hole a few years ago when I got held up by some guys and was psuedo-kidnapped. Its illegal to make arrangements with them in public, including electronically. Technically half this forum is breaking criminal code but I suspect LEO turn a blind eye so they can lurk. SWs don't have anything to worry about for the most part, it's legal for them to sell but it's illegal for clients to buy (try wrapping your head (both of them) around that).
Its illegal for them to advertise publicly, including electronically but privately is fine. And it's legal for you as the client to make arrangements privately, including electronically but once you make the transaction for sexual service you have committed a crime. This is why most of it is skirted by saying you are paying for time instead of services but good luck convincing the judge on that one if you ever need to explain yourself, and any of your subpoenaed information.