The main effect of legalizing the prostitution of women is and will always be to simply make it more common, not better. While we shouldn't penalize women for working in prostitution, purchasing sex from someone is not principally different from raping them. It really isn't. That's making someone have sex with you who almost certainly wouldn't otherwise, and mind you strictly on their terms at that. That simply cannot be allowed in my book.
As to what should be done with those who are displaced, robust exit support services that would offer temporary accommodation, help in applying for crisis loans or disability benefits, counseling, advocacy, and advice are required to help women successfully transition out of the sex industry and into other fields of work.
(Concerning anal sex, what I have spoken to is the rule of how it is experienced. I won't get any popularity points for pointing this out, but the simple truth of the matter is that the nature of authentic female sexual pleasure tends toward the unfashionably vanilla. And no, I'm not for outlawing anal sex or what have you. I pointed out a connection it's growing commonality and the proliferation of online pornography as part of my larger argument against pornography as an institution and proposed that online pornography should be blocked.)
"purchasing sex from someone is not principally different from raping them."
One involves getting permission, the other doesn't.
The two are different.