Using acronyms or various euphemisms doesn't change the fact that [strictly speaking] the exchange of money directly for sexual activities is considered illegal in nearly all of the US.
That being said, that's not really a problem in itself. Proving that someone solicited the exchange of money OR something of value for sexual services in it's strictest form is exceedingly difficult with exception to a few scenarios. Those scenarios are namely: getting caught propositioning a cop on the street/car, or, busted in some form of surveillance/sting operation. There are maybe a few other very similar situations but basically it all boils down to someone being caught on some sort of audio or video surveillance or by the testimony of a police officer.
However, absent those situations, it's almost impossible to undoubtedly prove that someone agreed (simply) to exchange sexual favors for something of value. In fact, even in some of the situations above, it can still be terribly difficult to prove.
Why? Because technically speaking sex with anyone is quid pro quo. That's a Latin saying which means quite literally, "something for something" or "a thing for a thing". More commonly, "you scratch my back and I'll scratch yours.".
All sexual acts, sexual relationships, and for that matter all relationships, are based on the exchange of something of value to each person. That's the entire point of any relationship, sexual or not.
When you go on a date with someone, a regular date, the man may pay for dinner, drinks, entertainment, and more. You may have a great evening together. You both enjoy each other's company. He likes her brains and beauty. She likes his financial ability, swagger, and handsomeness. You both like the same movies. She is super kind and compassionate which captivates him. He is super funny and gregarious and makes her laugh which she desperately desires.
If sex is involved at any point now (using the strictest definition of prostitution) these two people have committed a crime. Things of value were exchanged. Many of them. And in this case they were exchanged for sexual favors. In fact, some of them were directly financial and cash based. Even though this was a totally "normal civvy date". All relationships share this basic dynamic.
Okay, that having been said, is what I've described a really sugar coated form of circumlocution to get around the heart of what prostitution is about? Sure. Is it just a bunch of fancy elocution? Yes. It is. But any good lawyer would use this and it's effective because it happens to be the truth.
Prostitution is very poorly defined and even with a more rigorous definition it still doesn't escape the same core issues.
Point being? If you are careful, actually "proving" that a true form of prostitution, on either side, occurred is pretty difficult, if you are smart, except in a couple situations mentioned earlier.
-MG