No. It won't work. Hear me out.
Apartments have multiple levels, so there can be 16 rooms (Or instances) per apartment building. When multiple people owning the same apartment join a game, they get placed into their own separate instance, which can be on another floor, or to the side. Garages work by placing them under the map near the apartment. There are very few underground obstructions (Subways, etc), so it's a perfect place to put them.
Mansions (Or other private residences) are just one property. You can not have multiple instances in the exact same location because this will only lead to a whole host of glitches (You try to drink a glass of wine but another player randomly pops up in front of you and keeps drinking, you have a random stripper that you didn't call for dancing by a chair, etc). You can't just move the instance up, down, left, or right. The view from your window would not correctly align with the exterior of the house.