Later I had to redo the electrical and I had to redo the insulation in the attic as the tenants were complaining in Winter.

If original, the insulation on that wiring is at about three times its design lifetime. 

Many of these types of companies do use SIPs or a similar highly insulated panel. 

Do they have the new double wall insulated tanks or the single wall? 

Gettting an attic completed ends up costing quite a bit- with electrical, permits, architect, heating, insulation, etc. 

When they find out where it is at or do not know where it is at and drive there that's when you hit the problems.Control of the area to insulate your investment is key.

After a drain system and sump pump is installed, then I what to do the following before putting on the drywall and insulation. 1) fill any holes on wall by Dryloc fast plug2) paint the whole basement wall by dryloc3) install the special water proof drywall used for the shower area in bathroom.Does this sound good?

During my walk-through, I noticed that there is mold in several places -- including the ceilings of two bathrooms and around the frames of most of the windows.The house has been empty for a while, the windows are not well-insulated, and the bathrooms have little ventilation, so I'm not surprised that mold has started to grow.

It needs far more work and updates then I ever realized, I only looked at it once in person and started the purchase while out of state.It needs new windows throughout, it is not insulated, it had knob and tube electrical behind plaster and lathe walls, the layout leaves a lot of poorly utilized space, the garage roof was trash and required a new rubber roof over a really weird layout, it has a single steam boiler for the entire building 😣😣😣Did I mention terrible rental market?

And be sure to look in the attic to see if it needs insulation and check for leaks, basement for leaks and water infiltration and crawl space.