They would ask the perimeters & send a pdf list, cd & even labels.

You can check with USPS if there is a forwarding address or if it is labeled as vacant.I have found many this way and from services like Reiletters 

As an example, if you're mailing to unsophisticated homeowners, they might throw out a #10 white envelope with a corporate address for the return label and stamped by First Class Mailer.

"They are intrigued" There are lots of authentic mail pieces you can use including stationery, that has choices of return labels, or hand-written. 

Sometimes these old detached garages in Phoenix are labeled as “workshops” on the assessor’s site and therefore they list the square footage on the site.

I have always used a standard Rental Agreement that I would for the entire house, BUT, you need to identify each bedroom (1, 2, 3 or A, B, C) by labeling each room, and then reference the room number along with the property main address on the Rental Agreement.

Use Watt's Law to calculate usage if the label only shows amps to get hourly usage.

Many of them had realtors (whom I would personally label as predatory) telling them it’d only be going up from here and it was now or never to buy if they wanted in.

@Kelly Claiborne - I'm going to assume (probably wrongfully assume) the popular answer will be some combo of knowledge and fear - and I'd label it as perceived lack of knowledge that causes fear.  

If they do this, they then will label all your transactions as dealer status and therefore tax you differently.