Keeping 6+ deals together at the same time is a lot of plates to keep in the air, and finding properties to buy (with so little inventory and so much competition) ends up being the most challenging part for many investors. 

We have a few furnaces to replace and AC's to install (possibly- see below).2) What does everyone estimate the value of central air to be in a upper-medium-end rental in Minneapolis?

An older building with poor insulation and a lot of air leaks will be challenging with a mini-split.

I'm sure these are low-income tenants who aren't suddenly going to be able to pull another $300/month out of thin air. 

I’m a U.S Air Force combat Vet and an investor and licensed Realtor here in DFW.

My father bought a 1964 Barracuda that we intended on restoring, but instead I had a S-10 that I put a bunch of money into (air ride, wheels, etc.)

One of my investor clients bought a large ski house and rents it constantly on Air BNB, she may be open to chatting with you about her experience with that business model and she lives just north of Boston.....hers sleeps ten though, so  a different property than what you're considering.

The sellers recently installed new forced air heat in all the units and the electrical service has been upgraded.

Not sure what your budget is but I would get a property that you can Air bnb.

Anyone interested in splitting the costs of a VA for Air BNB?