I am not in an area that is zoned commercial so perhaps that excludes a "Commercial" label.

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

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

I compare this to the HUD laws that popped up in the 1980's and my mentor's mentor, Abie Label's mindset at that time.

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.

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

Ditto...ordered labels with our box address printed and put them on a year's supply of envelopes for each tenant.

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.