it's strange that you want to avoid a slippery slope leading to women having their bodies controlled by others... by telling women what they can and can't do with their bodies.
It's not at all strange, slightly ironic perhaps but really not that difficult to accept - we/society/government tell people a lot of things they can't do whether they want to or not to avoid their own or someone else's freedom being affected. Massive actually brought up some perfect examples;
It would make no sense to outlaw marriage or staying home with the children simply because there are endless anecdotes of it ruining women's lives. Same goes for prostitution. (outlawing sex because some women's lives are ruined by it would be silly as it doesn't inherently contain that element but selling sex is the issue)
You can marry, broadly speaking, whoever you want for pretty much any reason you want - because you love them, because they have a nice face, because they like cats. Try marrying them because they're paying you however and you'll find there's laws against it, however much you might like to. Same for having children with someone - you can have kids for almost any reason with no hurdles at all (legally, unless it's underage or incest) but there's again some hefty laws about being paid to have kids, because we recognise some things should not be for sale. I believe sex is one of them (as far as actually enforcing this though I've already said I think the Nordic model is best).
I may decide having an arm chopped off would be lovely and ask someone to pay me to allow them to do it - I'm not allowed to though, not because that's a weird double standard but because we have to balance personal freedoms, the freedom to choose against freedom from harm in this case.