That said, I would strongly advise that you get a lawyer involved, or at a minimum a licensed Realtor (you mention "brokering" the deal, and that you are a SWE for Google, but not that you are a licensed Realtor...if you are then disregard that last part).

Think whether this ADU makes sense financially for you, and should you also get tax benefits, then it's a nice bonus.

The big question I have is, will I be able to transfer this into my LLC which then can be used as an investment to avoid/defer tax? 

Earn more, spend less, save, then invest.

If you provided AC, then your obligated to keep providing AC.Service call fees are standard for pretty much any type of contractor. $200-300 is typical in the larger metro areas.

And yes I tend to do that sometimes... start with just one question and then think of a second one while the fingers are doing the typing!

You then have to stack your financing costs on top of that, as well as reserves for Maintenance and Capex.You could always start off offering the other side of your house as a STR and see how it goes.  

If you are out of state and trying to do a major rehab, unless you are in construction for your full time job then my recommendation is one of the following:1.

But, if the equity is a useful tool that helps me complete BRRRRs then I would consider moving forward with the farm to keep it part of the family.To those with more experience: What would you do?

I would try repeating what you did a few times and if there's success then you know you're on to something and maybe you can teach that to others.