Knob and tube wiring, no insulation, old foundations, etc etc.

Practically speaking, that means that any safety issues (unsound structural items, unsafe wiring, etc.) and "broken" systems of the house (plumbing, heating, insulation, etc.) will need to be fixed.

With only one property, it depends what else you have to insulate from it in case of liability.

In late July he came in and insulated the ceiling.  

I love Boxabl and plan to invest in them so I think that's an awesome plan...but I find it hard to believe it'll be cheaper than finding a good contractor to frame out a bathroom/kitchenette and insulate/sheetrock a garage.

I spray foam insulated the building with the first two units but the $750 building the tenant has stored too much in his basement so once there is turnover I will do that basement.

I am in the process of building an AirCrete foaming gun and molds, with the intent of making insulating blocks of light weight, low density, low-to-medium strength concrete.

And should there be any slowing down of the single family market, commercial assets, particularly in sectors such as multifamily, self storage, and mobile home parks, tend to be less correlated to the market sentiment, thereby further insulating investors from market downturns.

The good thing about this property is its insulated so well that everyone gets some benefit of the others heating/cooling.

Drywall, Paint, Insulation, fix cabinets.