I wish we could get photos of some of the crazy stuff that appears to be going on inside the unit, but getting in those areas is difficult, even without a camera.  

The least destructive way to check for a leak would be to insert one of those fish cameras into the register (like the ones used in cars to check cylinder condition).

The property came with security cameras and a Ring Doorbell.

Some of the photos in the listing were okay, but flip your camera as people are used to seeing things wider than they are tall (ie landscape orientation, not portrait).

Being a plumbing contractor, I have many real estate investors who call my company to do plumbing inspections and they want us to put cameras in the drain and sewer pipes.

Our biggest mistake( after that we did not put the cameras all over the house, until it would be sold ), our biggest mistake was, we never actually have read the policy, with the foolish confidence that we will never need it.

I hired a plumber locate the pipes and run a camera but he said he cannot see because they are full of muddy water and he cannot locate the pipes because of water in them. 

Leave the lights on, and cameras help.  

He went back the following day and he said the sewer line/drain had clogged again and he was going to get a cctv camera to troubleshoot and see where the problem was.

I would also add security cameras to document any additional damages.