Prostitution is already the law.
What is illegal is making a fair cheap strictly limited deal between two consenting parties for xx services and xx payment.
The whole "marriage" business as enforced by the Communist corrupt courts is basically high priced prostitution/slavery ring designed to enslave men, for the most part these days where the guy "maybe" gets some sex for a bit and then has to pay with an unlimited amount of his cash & be a slave for who knows how long, enforced by the courts even if he stops getting the sex he thought he was getting & the other party goes starts enslaving another person.
Or like half the women on the dating scene, they expect the Man to spend a significant amount of money on their "entertainment" and "happiness" as well as "gifts" and other such stuff, then they might do sex with him till they find another deeper wallet..... Perfectly legal.
What is currently illegal is when one party is honest and fair up front and says ..."You want sex... normally you'd have to spend for flowers, dinner, movie, gifts etc... Just give me what that would cost up front instead and we'll do the sex & I'll then go spend the money on whatever I want".
Prostitution should be completely legal. In many countries around the world it is legal.
Where you have to regulate things is when it comes to others living off the proceeds of the prostitute, to avoid them being victimized by pimps and criminals, however when it is all legal and out in the open and prostitutes have the full protection of the law, it's a lot better for them, as they can ask for police assistance when things go wrong.
That being said, being involved in any of the sex or sexuality for money thing is one of those areas where some really enjoy it & have a decent time & get rich, many others find it to be yet another soul sucking nose to the grindstone pain in the ass job where the promises of quick money always seem to be just out of reach.