Using a thermal camera part of your pre-purchase building inspection can be a vital tool. Yes the cost of the inspection is likley to increase but the benefts outweigh the extra costs.
Thermal cameras can pick up heat differences within walls and ceilings, it could be either cooler or hotter which can be caused by moisture leaks or even termite infestations.
The image in the post is a shot of a bathroom wall. The house was only 8 years old and it is evident that there is a waterproofing failure.
The darker the colour means colder and the lighter/brigher is warmer.
If possible ask for thermal imaging camera to be used on your building inspection for the property you are looking to purchase. For the extra couple of hundred dollars it could save you thousands in repairs and atleast give you the opportunity to negotaiate on the pruchas price.