Then what should be done?
Nothing. As I said before: prostitution simply shouldn't exist as a legal concept. Since prostitutes aren't, in the legal sense, harming anyone, then prostitution shouldn't exist as a concept in criminal law; however, since sex can't be exchanged as part of a business contract, then prostitution shouldn't exist as a concept in civil law.
Simply put: the government should ignore prostitutes and their affairs entirely as a non-entity.
Footnote:
If the problem is that prostitutes are vulnerable, abused, etc. women, then our concern should be making things better off for the least well-off members of society, shouldn't it? Of course, the richest members of our society wouldn't like that, would they? :nono:
What should be done? Legislation that imposes a very rigid standard of fairness upon all business transactions (including employment). And where that fails? Social programs.
Simply put, if a man can't live a good and decent life off of what his employer pays him, then the employer shouldn't be able to hire him. And if employers just stop hiring? They should be obliged to pay taxes to make the poor better off anyways.
Also, lots and lots of tax funds to education. Everyone should be able to get educated (up to and including a Ph.D.) if they want without having to pay a dime. Just saying.