Here are some questions to Krogith.
Exclude all the girls who are forced into it at 13. For the purpose of this question, they are peripheral and irrelevant.
Let's say there was a girl who, after leaving college, decided "OK... what job should i choose now?" and made a deliberate decision to become a prostitute. Is that wrong? And is it wrong for men to hire her?
Next question:
Same girl thinks "OK... what job should i choose now?" and decided to work at a strip joint to make money while she looked for a real job. Eventually she ends up in prostitution and doesn't bother getting a different job. Is that wrong? Is it wrong for men to hire her? Or is the key issue whether she likes it or dislikes it, and whether she continues because she has to in order to keep a roof over her head or continues because she doesn't mind it so much and doesn't really want another job?
Finally:
Let's say the girl, instead, got a job in a fast-food place. Limited pay, unintelligent work, long hours. She then doesn't have the time or energy to find another job or the money to pursue a new qualification with the intention of a different job at the end. Is that wrong? And is it wrong for people to order fast food off her?
@InfinitusEquitas: Haha... oldest profession. Meat-sharing hypothesis
I like your idea though. They could run a drug-test on all the girls, and ensure they were on contraception and check appropriate documents to check they were of-age and in the country legally. Then the women book a spot in a venue in which they could "advertise" themselves in the hope to get hired, and upon doing so they would have to verify in private with no others present to a trained counsellor that they were of age and that they were doing what they were doing voluntarily. The counsellor could have contacts in the police, so that if there was something bad going on the police could go bust the guys' chops. To enter the venue a man would have to have a CRB check, sign various documents and have a medical record check to obtain a pass which he could present each time he wanted to enter. All private rooms would be fitted with panic buttons. Haha... this set-up works!
So the rules
can be enforced! Krogith, try to pick holes in it...
EDIT: @InfinitusEquitas: Chez loves her long hard objects, especially if they produce emissions.