Take, for instance, a Best Buy. A Best Buy could potentially house hundreds, especially considering the vertical space (think bunk-style shelves for sleeping). I'm not suggesting this is good or that it would be comfortable, but we've got more than 4 million people working retail in the US, and retail is going nowhere fast.
IOW, in the markedly more dystopian future that I imagine, a lot of the same people that work in these big boxes will live in these big boxes.