Adults have the abillity to engage in free enterprise, as long as all parties involved consent I see no issue.
Regarding sex, the only times you get to have oppinions about another persons sex life is...
...when you are part of it.
...when it involves underage people.
Why should money be a taboo reason to have sex? You don't get to pick and choose what motivation other people have for sex.
You don't have to engage with this type of enterprise if you don't want to, so leave other's alone.
In general, prostitution will allways happen, you can try whatever laws you want, but you can't stop it. The only thing prohibition acomplishes is to deny sex workers the protections they need to stay safe.