It sounds like there is one furnace for heat and HW, so you're paying those costs. 

If you are heating and cooling the space then yes you are adding heated square footage.

I contacted some mitigation companies today and it looks like $3-4K to have a "ambient" treatment performed where they heat all units to 130+ degrees for 5 hours and then spray with chemicals. 

Cleared permitting issues and brought electrical and heating to compliance with post-hurricane building codes.

It has that and one boiler for heat.

Knob and tube are not safe because the heat form the electrical current over 100 years breaks down everything becomes brittle /FIRE Hazard!

We're doing the following: Bathroom: drywall, heated flooring, tile flooring, double vanity sink install, glass shower install, clawfoot tub fixtures/plumbing install.Denver area recommendations are greatly appreciated.

You can take a look at realtor websites and see what's for rent in the area you're buying and have an idea.Also keep in mind, the non-separated utility meters (water, heat, yard maint) is paid for by the landlord in MF. 

There was no plumbing (stolen), outdated electrical, no heat/AC, unfinished attic and a bad layout.

The first house has oil heat.