When I was a kid growing up in Vancouver, we lived in a variety of apartments buildings that were aimed at families. These buildings were full of 2-4 bedroom units clearly intended for families with kids. Usually 3-7 story buildings with anywhere from 6-100 units like this. Now, granted, these were buildings with apartments for rent rather than units to buy, but the layout concept seems the same. So I'm not sure that what's being discussed here is anything new. Families that are not affluent already live like this, in "stacked homes" otherwise known as "apartment buildings".