Ghosts are still anthropomorphic fellows and gals, yes. 

There is nothing that makes them against becoming slaves. There have been cases where ghost youths have traveled away from their isolated desert to find settlements and some of them settle down with non-Ghosts. So there's a lot of option with that.

I haven't considered binding it since most non-Ghosts see it as "myths" and not reality.

As long as the aspect of low magic in a manner that I approve of (no fireball slinging; "magic" isn't fantastical).