All that time with no heat in the winter and no air conditioning or ventilation in summer can cause moisture to form in the structure due to condensation build up.

As far as install goes, it's not particularly difficult but improper installation can cause issues with moisture and air conditioning leakage. 

"I've got a guy I can recommend that will come out and measure moisture levels in the walls.

Seals up airs gaps and blocks moisture but doesn't let house breathe and if applied wrong can have negative effects.Obviously would want something I can do myself and achieve a price lower than the $1,000 for blow but want to make sure it is effective.  

Identify where the moisture/humidity is coming from.2.)

I had a new master bathroom installed and I have started to suspect moisture is gathering in that attic.

There is a carpet pad that has a moisture barrier that will prevent pet urine from penetrating the pad.

OK< so a house with plants on the wall to the second story (so moisture on the siding) and a large hole in the ceiling (prob water leak) is a minor repair and only $135K in Eureka?

It looks like you have good eve coverage over the walkway so moisture issues may be minimized. 

was the dehumidifier part of the hvac system to remove excess moisture?