Beware of anyone who tells you that there is a way to word things that will prevent you from being prosecuted if enough information is exchanged so that the guy knows he is going to get laid for xxx dollars...  You simply cannot "talk around"
or retroactively make the deal go away.  If you could, you could legitimately take their money for time spent together, have no sexual contact and then say good bye when the time is up.  Everyone knows that is not what is going on.  If you do that you are not breaking the law.  But you will be putting yourself out of business.  The test is whether a reasonable person under the circumstances would know that he is paying for a sex act, plain and simple.  You are taking a chance, that is the long and the short of it.  So is the guy, although there seem to be fewer sting operations aimed at the hobbyists.  Can cops use the internet escort resource to find providers to arrest? Of course.
    Put yourself in the shoes of the judge...officer says he saw photos of escort on website.  Called, emailed or saw "rates"
on website.  Made an appointment.  Came in, put the "donation", "gift", whatever you want to call it, on the table.  She took her clothes off and she was in a thong and T shirt.  He says "blow job first or sex?" and she says "either way" (or whatever other response she makes, or no response, just starts to approach him.  Sorry, sweetie, argue there was no act of prostitution until the cows come home, but you are busted.  The judge does have to exclude evey reasonable hypothesis inconsistent with guilt - but just what would it be?