In the right areas with the super big townhouses you see a lot of 20' x 80' x 3 story (10' per floor) houses that have theoretical square footage of up to 6k sq ft including the basement. Obviously walls, framing, stairs etc are gonna take a chunk out of that, but these houses were built for intergenerational families 2 centuries ago, and are generally meant to hold up to like 10 people let alone four and two dogs.