Of course, as a cover my a$$, I have to say that I have not evaluated your specific situation and this advice is just general in nature and you should consult with an attorney in your area.

Really looking to supplement my current income with some passive income from SFH. 

 Short term rentals in Nashville Davidson county can only be held by a natural person, no LLC or any other entity   Also, owner occupied only.

In addition to the lessons you have already learned, a couple of mine:1) Natural curiosity - especially about "boring" things - can help you learn the vital information to move you forward2) If you don't know, ask someone, and/or do your own research.

I'm not pessimistic by nature, I've just been on the planet for over 50 years, and that's more than enough time to see what all can go wrong with best-laid plans.

One of our rentals has hot water heat powered by a natural gas furnace.

Given the historic preserve nature, I can foresee rehabbing these older homes with a ton of red tape associated with it.

I do realize that a partnership and JV are different animals, but I didn't know which was more suited to this situation with the on-going nature rather than being a one-off.

Almost everyone would say that you change the nature of the property and actually create a new piece of real estate when you build on land you own. 

Less concerned if it doesn’t unless the violations are of a nature that could land them in jail.