Buy a property with lots of bedrooms and rent out the spares to family, co-workers, friends?

I would keep reaching out  (emailing is preferred, so it's in writing) to the county permitting department until you get a clear answer, even if it is "We don't have any occupancy septic rule". 

It wasn't and we had it permitted.

Hi,I have a permit to build a 720SF ADU in Oakland.

[Realtor.com]Starts & Permits: Long-term PerspectiveHousing starts disappointed in July 2024, falling 7% month-over-month to 1.24 million units (SAAR).

Realistic timeline 6mo not including permitting.

Is the city issuing new permits? 

I know from experience it will go nowhere because it's not illegal.If you were charged fees without your permission, or not permitted to be charged in your contract...then that would be illegal.

I’m aware of permit requirements in my local township, and I would have to follow up with what’s required in the location of the investment property. 

Furthermore the local experts can confirm the following: (1) the use is allowed, (2) the use requirements can be protected by permitting and licensing and (3) the permissions are transferable through a sale.