This is important to know but can be lied about very easily.

The unit was installed up to local codes and the technician, instructed the tenant that the filter needed to be changed and Bleach/ Vinegar added to the drain line every 30 days.

sounds like something you can easily do with excel or google sheets.   

They are bought and sold quickly and easily - just like a car.

If only the exposed vent and drain pipes in the bath could be so easily resolved, they're actually solid brass, maybe I should polish them out!

It has info in it like: trash removal info, emergency contact info, how to operate the fireplace, how to change out furnace filters, parking info, how to get renter's insurance, local phone numbers, move-out checklist, etc.

FYI, if it's only water stains(brownish spots), and not bad drywall that will need removed(like if it's sagging or you can easily break thru it), then you can paint over it. 

Now it can easily blow way past 100. 

(how and when to change filters, how to run the sprinkler system (if there is one), where is the water shut off?

If you’re investing in Dothan I would look to roll your free and clear home into a loan on a bigger property that could easily rent to the pilots that are constantly rotating through there.