Would it be possible to let them send wisps or messengers? Certainly charge for it, but it makes sense (at least to me) that if you're wealthy enough to own the house, you're wealthy enough to communicate.
Additionally, it would be really neat if you could "upgrade" their food/drinks etc. to be able to sell maybe bar system stuff, or healing potions, or whatever, for an investment of gold/time/xp/insert-thing-here.
Thanks!