But anyways, I have a stretch where I’ll be gone for several months - mid July through mid October, possibly stretching to the end of the year, and I’m wondering if anyone has any ideas beyond just a normal rental - traveling nurse, etc. that might be good in Nashville. 

So shift your expectations to most of the cash out and you'll be good and you'll actually start buying deals, versus people who wait for the perfect deal, spin their wheels for 6 months terminating contracts/analyzing hundreds of places, and then eventually burn out and give up. 

Expect a custom ADU to take 9–18 months, with 3–6 months for design and permitting and 6–12 months for construction, depending on complexity and contractor availability, and the speed of processing permits.

- Go look carefully at the numbers and you'll see this.If you could acquire more rentals and they threw off $500 profit each/monthly, how many would you need to make a living?

It'll likely take a month or two assuming that the loan is with one of the large servicing companies that move at a glacial pace. 

Make sure you talk to a Banker or Loan officer that is well versed in both SE (Self Employed) income and also Non/QM programs.One tip I will give you as a Banker is open up a "Business Checking account" and for the next 12 months pay "Everything" out of that account. 

Can I charge them fees & rent for storage of their crap? 

For families, amenities like a crib or high chair can make your property stand out.Tracking Booking Impact: When adding a new amenity, I monitor changes in my booking volume, nightly rate, and overall revenue over a 2–3 month period.

You can get some estimates from contractors for what they charge for big ticket items like to renovate a bathroom, renovate a kitchen, replace the furnace, replace the roof, etc.All wholesale deals should have free and clear title and you should be able to see the sales agreement before submitting the earnest money deposit.

The structure would be a 75/25 profit split with projected returns of 10-15% on your money in 4-5 months.