I think prostitution law *should* be an issue left to the states. It's one reason I'll likely never vote Libertarian. Some (L)'s, and perhaps even the party platform itself, support making prostituion a "constitutionally protected right" like SCOTUS did recently with sodomy.
I don't understand how the Court's stance on same sex sodomy laws cannot apply to prostitution laws. Was it "equal protection" (men and women) or "privacy" that they ruled on?
Prostitution occurs between consenting adults and there are no more fornication or adultery laws prohibiting sex between unmarried partners. The financial aspect shouldn't change things; it is not illegal to hire someone (even a minor) to provide unlicensed child care in your home (a babysitter).
So if you can have sex with someone you meet in a bar and you can pay someone in your home, why can you not pay someone in your home who you met in a bar?
If morals laws, sex laws, privacy laws, and consenting adults are considered, there is no law.
As to "equal protection", homosexual is defined by an act, not gender. 2 men were prohibited from committing same sex sodomy just as 2 women were. Any man and any woman were permitted to have consensual sodomy with each other in Texas.
Since the Supreme Court struck down ALL sodomy laws (not just those that distinguished between heterosexual and homosexual), it wasn't on the basis of "equal protection".