So this is definitely a good place to be for beginners.

Ultimately, if you come across an MFH with a vacant unit that suits your needs for residency, it's definitely worth considering and I encourage you not to hesitate.

Is (Subject To) real estate sale legal in California?

How can I introduce them to the proper documentation to and legal process for this?

If you have specific concerns then definitely discuss with an attorney. 

I definitely second learning a market and what makes properties do well and poorly in that specific market.  

I've never done this before, we usually just ignore the LLCs, but honestly its worth a try, if I were a lawyer I wouldn't disclose anything about my client but I would definitely pass on the offer.

@Susan Walsh I agree....after writting my thoughts out on this forum thread and getting inputs from you amazing folks, I realize that STR by the room is definitely more challenging and fraught with risk.

Find building restrictions, structure plans/design, financing, legal issues....

I’m what about contracts/legality?