I live in an 1100sq ft townhome with both my girls and the cats. I take the girls for walks everyday, 2 times a week they go to the field behind us that is fenced in and run and play and over the weekends we go to the dog parks, usually on saturdays. both my girls are fine. Luckily though they are pretty much coach potatoes. They love laying on the floor and watching tv, or running up and down the stairs if they get bored
we also have a small (and i mean small) back yard but they dont typically go out there. they love staying inside.