If the houses are worth something, you can always sell the tax deeds and avoid the legal costs.  

I'm feeling bullied and as if I'm being held hostage and am not sure what I can legally do. 

Does anyone know how this is defined legally in CA?

The absolute BEST (and most expensive solution) is a highly qualified attorney who’s a specialist in estates, because they will provide the optimum documentation, legal thinking, and specialized situation for every client.  

What is my legal obligation to close a property that's not listed by an agent?

This is correct, a lot of the FHA guidelines have changed in the last year making ADU financing a lot more acceptable and easier.

Removing Hassle: Take care of moving costs, dealing with tenants, or assisting with legal paperwork to make the process smoother for the seller.11.

- How should we structure the deal legally for a BRRRR strategy?

Without responding with respect to your zoning and what is allowed locally, I will discuss what is allowed on state level because i believe it will allow what you seek.In 2025 SB 1211 (Skinner) – Multi-Family goes into effect allows an ADU (I think it specifies detached but question if that is a requirement) for each legal non ADU unit up to 8 units.  

I understand STR is not legal in Oakland, but yeah the unit is on the more luxurious side.