https://en.wikipedia.org/wiki/Duplex_(building)
They were popular in many cities in the 70s as starter homes. The idea was that you'd buy the whole thing, then rent out one half to help offset your mortgage.
Obviously this lot-splitting may not work in areas like Los Altos where each single family lot by city law is required to be 10k sqft or larger (unsure how local laws will interact with SB9).
But question @koolba asks is still valid - can you recursively split large lots into many smaller lots?
But that's not the same. Ending RH-1 would mean something like "no more RH-1 buildings will be permitted, you must build at least two". Instead, it's "if you have an RH-1 lot, you are allowed to build up to two units".
So I'd say it makes RH-1 also mean RH-2, but doesn't "end" it in the sense most people interpret. (E.g., In San Francisco, you would be unlikely to get planning approval to build a single-family home on an RH-2 zoned lot, because it should have been used for two units).
> This bill, among other things, would require a proposed housing development containing no more than 2 residential units within a single-family residential zone to be considered ministerially, without discretionary review or hearing, if the proposed housing development meets certain requirements, including, but not limited to, that the proposed housing development would not require demolition or alteration of housing that is subject to a recorded covenant, ordinance, or law that restricts rents to levels affordable to persons and families of moderate, low, or very low income, that the proposed housing development does not allow for the demolition of more than 25% of the existing exterior structural walls, except as provided, and that the development is not located within a historic district, is not included on the State Historic Resources Inventory, or is not within a site that is legally designated or listed as a city or county landmark or historic property or district.
Source: https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml...