It is legal to have sex with any adult for any reason except to make money directly. You can do it indirectly if you are a clever bargainer. If people don't want to change this reality, then I think we should agree to legalize or decriminalize prostitution.
I personally favor strict regulation to protect the streets, and women in general. But overall we shouldn't have laws that ultimately are unenforceable.
Sure we can crack down on really big prostitution rings, but if a woman wants to have sex for money, surely she will figure out how to do it without being subject to the law.
We need to re-instate good moral values within people, and stop trying to play games with the law.
I support morality training, within the context of sex-ed in the schools.
But we know there will always be people who don't listen, and so in a free society we have to let people be free if it doesn't harm us.