I have to wonder if some of the more affluent neighborhoods/cities won't just find a way to stop this in their area. Does anyone have a sense of how effective this law will really be, particularly in cities with NIMBY attitudes?
I could see it making a huge difference in "affluent suburbia" - places like Sunnyvale, Cupertino, San Jose, the SFH parts of Mountain View and San Francisco, etc. The lots there are generally wide enough to support a lot split, and you have a lot of homeowners that just spent $3M because you need to in order to own property, carrying a massive mortgage. The lot split would immediately let them pay back a good chunk of that principal, and a duplex would give you rental income to cover most of the payment. A lot of homeowners would go from being financially stretched on 2 FAANG incomes to being comfortably able to live on one salary, while still maintaining ownership of a duplex.
Many of these neighborhoods are precisely the ones that need it most - they're close to jobs, they're flat, they could support a lot more population, and they already have significant pro-housing contingents. Traffic on 85 is going to suck even more than it already does, though.
That might happen in the really rich neighborhoods too.
You'd have way better liquidity too. It's hard to sell a $15M estate. It's significantly easier to sell a pair of nice duplexes, each on 1/2-acre lots with double ADUs on each. You could probably get more than $15M in total for them too, since 8 units with an Atherton zip would rent for a pretty penny.
Sounds like a good reason to WFH.
Lots of older neighborhoods in cities, however, don't have any such covenants.