Prostitution isn't something men typically resort to, to pay for drugs, put a roof over their heads, put food on the table for their kids. There must be a reason why. The homeless beggar on the street could be in a nice warm hostel, if he just...
Some do, but the punters, again, are almost always male.
We can rigorously defend the choice of women to sell their bodies if they so wish, but we should also question why men don't. Men are generally physically stronger then women, so the risk is minimized somewhat for them. And there's no chance of them getting pregnant. So the risks are materially less for men, yet they still don't choose it for the money, in anything like the numbers women do.
Is it because women don't need sex in the same way men seem to need it? Does anyone actually need sex, then? Is it because women don't feel entitled to buy sex from someone who wouldn't otherwise have it with them? Is it because men need to be aroused to have (PIV) sex, whereas women do not have to aroused at all for men to have sex with them?
I don't know the answers, but when you turn it around, you see some of the implicit assumptions society has around the way sex is quite different for men and women.