I never seem to have families rich enough for servants, but I did play a game as a live-in nanny once.
My sim was the nanny sim and i moved her into a house that had twin babies and couldn't cope, so her job was to look after them and do some cooking and cleaning.
When they grew old enough, I'd move her into another household with little ones.
Once, she lived with a vampire family and didnt know what they were until daddy vampire asked to bite her. She fell in love with him and had to move away before risking splitting the family up. I really enjoyed that sim, lots of cool story lines came out of it.