Billy Joel, who has not aged as well as his former wife, has a home so large, with millions of connected hallways, he has no idea what is going on within his property. It seems to me that if you could establish where someone like Joel tends to spend his time, maybe 1 or 2 rooms, then you could enter somewhere on the other side and set up a living quarters for yourself.
Obviously here, a large part of his dwelling was just storage for his various collections. One might also wonder about their personal safety within their homes. If you wander around a large estate I have myself felt like there are mysterious things going on- especially in the dark recesses. Recall Jon Binet. Someone killed her and no one knew, and thy didn’t even know if the person might still be in the house.