Why photographs with dates
Every disrepair or damage dispute is a disagreement about when something happened. Undated photos on a phone prove the state of a room but not the date, which is the half that matters.
What to capture
Room by room, with a note where something needs attention. A repair that gets raised in an inspection and then fixed is a much stronger record than a repair that appears from nowhere in a complaint.
Access
You need to give proper notice and get agreement to enter. An inspection is not a right of entry at will, and getting this wrong turns a routine visit into a harassment allegation.
If you would rather not do it
Mid-tenancy inspections are one of the services you can book instead of doing them yourself.