Insulating foam caulking wood whatever it takes to fill the cracks .

In order of priority for insulating/sealing up a house, the doors and windows are first, roof insulation 2nd, walls 3rd and underfloor (in cold climates) is 4th.

That should allow any peak demand to be attenuated until fewer people are using the system.An even better option would be an uninsulated tank like a pressure tank which would allow it to warm faster, but even the insulated water heater will work.

The type of work done would not usually require a permit like replacing missing doors, painting, replacing faucets, replacing plumbing shutoffs and associate external hoses, adding plumbing stops to every sink and tub, repairing a steel fence (this took a lot of time, required core drilling and replacing retaining wall stones), glue top stones on existing huge retaining wall (should have already been glued as the wall has a permit as it is maybe 15' tall), fixing a garage door, adding insulation, adding drywall to existing framing, adding a closet, yard cleanup, repair the built in BBQ, change of many door knobs, etc. 

Hellomy Brrrr house spends high utility bills($400 per month in Easten canada) and I'm thinking putting 2 inch foam insulation under siding when i install new siding.

Sounds like you are living in a condo that is really old in age or was poorly and incorrectly renovated.It's common in older buildings to have thin sheet rock and also the insulation used in the walls had a lower value back then.Over time the insulation breaks down.If you can hear each other between the walls it is definitely not a person issue it is a building issue.Good luck on getting them to redo the walls and insulate to fix the problem.Your best bet is to move to a newer facility with proper sound deadening.If you moved to a town house on the end unit then you would only share one common wall.In an apartment you can have people below you,above you,beside you, and with poor sound control can be a nightmare for a tenant.No legal advice.

I recently had a contractor try to charge me $300 of a $425 job to put insulation in an attic (for matereals).

We used a lot of spray foam insulation and caulk.

Foundations were not waterproofed and insulated like is required today either.

I also insure that my properties are energy efficient by insuring that there is sufficient insulation, good windows and good seals around the doors/windows.