It really worked well, although the thing that helped the most was the tenants not stomping around :)  In my research on flooring options, I basically learned that the #1 best layer of sound dampening is the insulation material and a layer of drywall. 

Mostly on really aged home that have cloth insulation on the wiring.

Avoid electric heat if you can unless it's cheap in your area and the units are well insulated.

Then, again depending on what type etc etc, install insulation boards (usually ISO), Membrane (NOT just 30lb felt!)

According to the inspector. the duplex has too much insulation and not enough ventilation in the attic which is where the inspector found the mold.

Also as per Ontario provincial rules, only the "liveable" space (ie heated and insulated as per Ontario guidelines) should be included in the sqft of the home.

One of the drawers in the fridge is cracked, but rather than calling me or replacing it he just kept shoving it in the fridge to the point where it has worn through the inside of the fridge to the insulation. 

Find the openings, seal and insulate properly.

It might be insulating the pipes near that trouble area, sealing drafts from the outside with caulk and spray foam, or even using heat tape to keep pipes from freezing.

My house would need a new high effiency hvac system , fire sprinklers , 2 by 6 walls , more insulation , electrical upgrades , windows , etc .