- Is there a real benefit if the ADU is under 750 sq ft?

You can find properties that can surpass or stay below the average as well.As for the overall market panorama, there are huge projects planned or under development.

when you find a deal and want to secure it, you put it under contract.

I understand that some prospective buyers have gotten under contract but later backed out.

Most of them are under $10.

Get a cheap course, join a good brokerage that has enough full time agents that will help you by taking you under their wing - that is going to teach you more than the course you buy and take. 

Quote from @Jonathan Greene: You are ready to share deals that you worked hard to put under contract with someone on Facebook? 

Rental properties are excluded from 50a6 law however lenders sometimes chose to follow it still as an overlay (additional layer) to provide protection because sometimes borrowers falsy their occupancy to exclude them from 50a6 law (like saying you dont live there and pretend living elsewhere when you in fact do as a borrower live at the aforementioned property).

She told me she owns the house but when I told her the county record it's under a LLC. 

This is why it is important to have appropriate insurance and even more importantly making sure your actions are not listed under exclusions in coverage.