So a nicely decked out  cabin I bet would rent real well for STR purposes  Not sure about permits etc..

Trying to go to companies directly is rarely going to be your best bet. 

It looks like networking and meeting people will be my best bet.  

I'm betting your numbers look like mine, and CapEx saving is eating up a lot of it.

Doing this like a brrrr I see as the best bet, for example my property does still have room for improvement adding a bedroom and bath to the primary structure and then the ADU.

The safest bet is to try to get a variance from Union City. though clever, your combined unit lease agreement would likely cause trouble if ever scrutinized by the Tenants or the municipality. 

And that gave us a feeling of security that allowed us to take "riskier" bets.

As you concede, you and your tenant buyers made opposite bets on appreciation over the 3 year period in setting the option price. 

I think the outskirts are you best bets!

To avoid partnership issues, 50/50 is likely your best bet.