I would bring the current owner with me and have a face to face talk with the building officials and get it straight from the horses mounth with the current owner being aware. 

A lady on oxygen walks by with her health aide, we say hi, and she goes to the lobby to wait for a ride.

Assuming me and the potential seller reach an agreement on price over the phone or by email, what type of document or form would I need to make the agreed upon price official?

Over the last year and a half I’ve accumulated 45 units and haven’t done any official background check on any of the placed tenants.

I agree with @Matthew PaulOne of my rentals is a 3 story house with 4 baths, it's 2 blocks away from my "Official" job. 

Airbnb is under attack in many cities but AIRBNB as a company will not assist in any legal battle and often lobby for things that are against a host's best interest.Many realtors support Airbnb.

See the official San Francisco Office of Short Term Rentals website here: https://shorttermrentals.sfgov.org/Best,Michael Young

Not in Texas, but you need to contact the zoning admin and verify what the property is officially listed as with the city.

I’m officially tracking your property to see how it ends up.

Usually they also require their official name to be the mortgagee on the insurance.Recently I received letters from a mortgage company for 3 of my properties where my purchase price was less than $100k each, but they want coverage for at least $160k.