Just going to point out, this isn't a new concept. It's actually a rather popular thing in Japan and other Asian Pacific nations. Tokyo in particular is a hotbed for this type of housing, but of course Tokyo is also the single largest city on the planet (36 Million people in Tokyo City Proper), so it's more of a logistical and feasibility thing there.

There's really no reason for this in California. It's more than feasible for affordable housing to be achieved in California. The problem is that EVERYTHING is so inefficient in California that the cost of everything is easily 10X any other area in the country (with the notable exceptions of New York City and recently Miami Florida). Well, that and the obvious money laundering going on to line the pockets of every California state politician.