I brought this up a year or so ago on another board. IMO, if you have less that 10K sq ft and 20+ acres, you don't live in a mansion.
A good friend of mine built a house with 11K sq ft but it was more for investment purposes. Because of where it is, he'll be able to sell it for double what he paid for it (and when you start in the millions, double's pretty darned good) when he moves after getting his kids out of the school. In fact, now he's looking at property up near me. I'm about to make my RE agent a very happy woman
