@Tom CamardaYou can get a portable air conditioner/heat pump that is rated for 400-500 square feet for $250:http://www.newegg.com/Product/Product.aspx?

Portable heat pumps work pretty good and I like ductless heat pumps and the higher seer models will do better in winter.

I closed on my first duplex property in December of 2016, but I'm also heavily involved in self storage/portable storage.

While a CMHC insured mortgage is portable, CMHC homeowner mortgage loan insurance is available on a maximum of one property (1 – 4 units) per borrower/co-borrower at any given time.

I also put in portable units in one of my really inexpensive houses in MI - cost ~$450  and the tenants love it, so I'm going that route for any future MI properties.  

Are portable garages any good?

If you ask your insurer, I'm sure you will get the same response.Those portable storage containers sound like a good option for your buyer!  

You'll be able to sign all documents via electronic signature or portable notary.

I've tried to acquire some over the years, but ended up not working out because the cap rates just didn't make sense in my opinion, so I have grown in the business via portable self storage, which has been awesome.

If you the area is a C class area, then window units and portable heaters might be perfectly fine.