We like to use pretty bright flashlights when doing what we do. If you take a bright flashlight and shine it down the side of the wall or ceiling, every deformity shows.
In the photo above you can see where the joints of the drywall are. This ceiling was kinda borderline. I wasn’t quite sure if this was a poor installation or if the roof leaked in the past and these are repairs. We still like to ask our clients to ask the sellers for any and all knowledge regarding who did the install and if it was repaired. If it was repaired, if there are any warranties associated with the work.
It is easy when you see a bunch of repairs.