Are you in the US? It tends to be different there than elsewhere. In the UK here, it's much more accepted to buy flats and live in them long term. In the US, it's looked down on because people hate sharing walls, hate the monthly maintenance fee you have to pay the building, and hate the resale value and challenge with resale in general.
Apartments can be an okay purchase but tend not to be an investment like houses have traditionally been.
Isn't a semi-significant amount of the per instance load in the database interactions though? I don't know if that's still true after some of the optimizations in 0.18, but by having your own instance, even 1 person instance, you no longer load the database of another instance with calculating hot/active/whatever for things you want to see, and you don't load it when you do pulls.