Dog owners come in all shapes and sizes and so do their dwellings. I wouldn't necessarily think that you need a larger home to have a dog in SF. If you know your breeds, you'll know that many dogs, including some larger ones, do not need lots of space and tend to lay around quite a bit. That is not to say that some people have not fully thought about the space they have before becoming a "parent" to their pet. I've also found that apartments here tend to be larger than in cities like New York so even if you're in a studio (a NYC 1 bedroom), there could be the right dog for you.