I have a finished basement in one property which has occasional moisture. 

While sealant can give extra water protection, it might also trap moisture, leading to potential issues like mold.

Also do you have to use moisture barrier below?

The issue with hoarders is damage to the property- hoarding can lead to pest issue, moisture issues and other issue that physically damage the property over time and can lead to big $$ repairs. 

Roof age and condition: Create a visual checklist to use during a showing for signs of moisture intrusion or past/active leaks and make every attempt to gain access to attic/roof sheathing.

9) Flooring10) Trim and detail work11) PaintMOST IMPORTANT - 1) Egress/Ingress - you must have the proper sized windows in the bedrooms, and an entry door that is to code 2) Moisture - since you're in a wet rainy area, make sure you have this covered firs thing!

But they won't offer anything for lost rents or agree to run a mold/moisture test at their expense. 

We had a mold inspection done and there seems to be mold and high moisture content in 2 bedrooms, the kitchen and bathroom areas.

Again, something your insurance agent is going to scrutinize.100+ year old houses tend to have dirt floor cellars (or crawl spaces), so moisture is a thing in the house. 

Hi Everyone, Do you guys know about the best equipment that is not crazy expensive to detect if a wall is humid? Do infra red thermal cameras work for that?Open to any and every suggestions, Thanks in advance!