Rules changed drastically!
The Mansion Baron aspiration can be set to slaves as well. Since the aspiration is dependent on the lot value, it doesn't matter which sim completes it. This also opens up options for your slave to muck about in the rewards store. But they cannot purchase youth potions to extend their lives (they're slaves, not Highlander).
I changed the "Age Unplayed Household" to "Uncheck." This will make sure that your potential slaves won't age up to Adult and then to Elder. Who wants a buffet full of old and tasteless entrees?
Pregnant slaves are the only one who can be moved out via Manage Household. Your vampire is evil, but not that evil!
That's it for now. I'm still in Level 1 of the Mansion Baron aspiration. Currently one slave in The Countess' lair. A pretty little thing to look at. Not sure if she'll cavort with him wink wink nudge nudge.