Next time on a MAJOR renovation project, I'd have the City of Johnson City Building Inspector join me for a pre-purchase tour to tell me what permits and what jobs they'll require of me.

Please note, units have to be registered (then renewal annually) with the Department of Planning and Permitting in order to be operated as legal vacation rentals.  

I know from experience it will go nowhere because it's not illegal.If you were charged fees without your permission, or not permitted to be charged in your contract...then that would be illegal.

Cities can require that the primary unit be owner-occupied at the time of permit application. 

Do I need permits if I bring in a mobile home or similar semi mobile structure?

Visit your court house, city hall, etc and see what you can find out about permitting and go from there. 

Investors often buy these properties with a plan to gradually upgrade units and increase rents, or even redevelop them down the line if zoning laws permit.

Vetting and screening vendors, ensuring your vendors are licensed and insured, maintain all necessary permits and licenses, maintaining appropriate insurance,  requiring vendors to list the deed holder as additional insured, execute contracts with indemnification clauses, being an active owner or have a PM who is actively checking on your properties to ensure there are no premises liability issues or property conditions that could lead to claims.

No General Contractor wants to do a remodel with the residents still living there....they will charge you more (they probably will not show it, but the prices will be higher because of the huge PITA factor and increased liability)I would wait until you have completely moved out and then just give them the house empty and ready to roll.....But you can get a Scope Of Work going and start getting bids...even plans and permits if you're going that far...

Explore assumption of the existing loan, if permitted