In that scenario, the notice given to you during the middle of May served to terminate the tenancy at the end of June (not some random day in the middle of June).

People use STRs for small vacations/ parties/ random travel just as much as massively planned vacations. 

People don't want to visit random neighborhood of Nashville, TN (unless they are trying to stay next to family). 

They do have some options for building up (see three story image below) but we created an apartment that consists of studios units, in the standard 16x74 foot modular home rectangle.

You may see some zip codes missing -- this is because Zillow didn’t have data on them in their public dataset I used.If you’d like to enlarge the image, you can open it in a new tab.

Just some random thoughts as I read your post. 

Everyone's "should I" is personal to them and some random strangers don't understand the details.

We are currently on a 3.75% 30 yr with 25 years left, Currently we can not add more to our debts to pay them off faster, what we can do is use the revolving line of credit from heloc to pay off big chunks of debts thus lowering our totally expense due each month and free up more cashflow, at the sametime as paying off our heloc and other bills, by having the HELOC we can start paying off debt we could not while paying off our home at the sametime.IE: we currently earn about 4500$ a month, and have 5200$ in bills a month, with the HELOC we can shave that monthly total from 5200$ to about 3000$ by using the heloc right away and putting putting our 4500$ a month in the heloc Attached an image of our currently bills vs have a 1st position heloc  once we have the HELOC we can pay off some major debt, freeing up cashflow  while putting 4500$ a month in to the heloc and taking 3000$ out  monthly. 

The cement brick under the house appears to be layers, but not mortared.The pic that appears to be under the decking, the randomness of the 2x4 would be a question for me. 

So I didn't pick a random Midwest market and now I know Indy much more to a detailed level.