You can use Airdna & other STR estimator tools to get data on potential income/vacancy based on your location and property size. 

Thus, they are appraised as such - valued based off the sales comp approach - i.e how much have other similar single family homes sold for?

It's based on the purchase price and will not include any improvements, reno, or increase in value since the purchase.

Is it based on days used for business, miles driven for business, or both?

The court forms do not track this type of eviction so based on your sophistication you may spend a considerable amount of time and if you are off in the slightest the court will withhold judgment. 

I think many others have touched base on a lot of important points such as price and seasonality.

Totally agree , and when a home inspector looks at a house built over 100 years ago and writes a report based on current codes . 

They will be one lease to a room.That being said, the nonprofit will be filling the house based on their need; I will not be screening nor accepting/denying applicants.

@Anthony DiSanzoIf you're looking for low entry point properties that will stay in demand with a strong tenant base, I'd advise you take a look into the Memphis market. 

You'll noticed I'm based in one of them!