There will always be bad actors, you will never regulate malintent away.

Be aware of any local regulations in Emeryville as well.Please make sure your 4plex isn't exempt from AB 1482.

The regulations in Chicago can be quite overwhelming, so I’m looking forward to exploring the opportunities in this area. 

I was looking into the cities regulations and it seems like mid term rentals would work.

Your definition is correct for "legal non-conforming".The "legal" part of "non-conforming" is dropped when it doesn't apply so most commonly people call these units "non-conforming", "finished", "in-law suite/unit", or "bonus unit".Non-conforming: Any property that doesn't meet current zoning requirements.Legal non-conforming: A non-conforming property that was lawfully established under previous zoning regulations and is allowed to continue its use.Based on his posts @Mario Morales is referring to a non-conforming unit.

Use some for buy and hold (I personally would prefer apartments rather than buying a few single family homes) and some for lending/trust deed investing.In either category, you must know what you are doing, know how to vet the investment, how to vet the sponsor (if investing in a larger fund of some sort), the laws and regulations on the lending side, how to investigate which areas to invest in buy and hold and notes/trust deeds for that matter.So as you have already said several times, lots to think about . . . 

I have a background in technology and real estate (I was a previous VC-backed technology company founder), so I am very tech-friendly, and I like to adopt solutions that streamline workflow/enable best practices. 

Only difference I see with my practice is outsourcing more services.   

Quote from @John Herold: Hello all, what are some best practices for LVP floor installation for a manufactured home on a permanent foundation?

We will continue to have an influx of transplants from high tax, high regulation states like CA and NY.