The next property I bought was a 3 unit rental property held long term and the next personal residence I bought turned into 17 new houses built in my back yard. 

It still would not alleviate the other issues with an ADU addition such as revenue out long (often many months) before any incoming revenue, the worse financing associated with the ADU, that it likely makes your primary a rent controlled unit, that it detracts from the primary even if it is just yard, that adding an ADU addition is work (likely more work than a BRRRR with much lower returns), etcCan you post the valuation you receive when you receive the appraisal?

About the only thing I would do today is buy a nice home for cash in my back yard under market value that I could easily repurpose into a duplex. 

Sometimes it's better to start in your own back yard to mitigate rookie mistakes.

I am talking to a higher-end builder who lives literally 300 yards from my cabin.

Once you have leases renewing you can make emptying the garbage you put out part of the yard maintenance for the tenants to complete.

Nice mixed use property came up for sale practically in my back yard in rural, south of Pittsburgh, Pennsylvania.  10 residential apartments + 3 commercial spaces. 

But big back yard, detached 1.5 car garage.

I have seen a few scary things like "you need to dig up the entire front yard" in other groups but I'd like to hear from people that are actively investing in the city, and meeting the new standards, as to what their experience has been.

At some point ya gotta get real that the person who keeps shating in your yard isn't trying to help fertilize the lawn, there just an a-hole.