Zoning for David's Sample Deal in Show 598?

[Chuck Carlson]

In show 598 David goes through a sample BRRRR he is doing on a hilltop in an exclusive town in the Bay Area. My question is, how is he able to hack a single dwelling into a handful of dwellings? If the house is on a hilltop at the end of a cul-de-sac, I would think the zoning has to be some sort of low density single-fam. How's he essentially convert it into multifam? E.g., he added a kitchen for each dwelling.