Currently I play in a small dining room, and it's a little too small.
When I DM, I DM in a basement. The basement isn't finished, but it's all wide open. We have between 7 and 12 players at any given time and really need the room.
Ideally, I'd build a small second house on my property. Basically, a small kitchen with a bathroom off the side, a small bedroom in the back, and the rest of the main floor would be a huge gaming area. But, that's never gonna happen (oh wait, there's a lottery drawing tonight . . . ).
Dave