As Scott said, any form of leak,
Water damage is what kills most units, be it mildew, mold, rot, or delamination. Water is the enemy.
Open every cabinet and look for any indications, wear hard soled shoes so you can better "feel" the changes in the floor.
Along with the threads mentioned above , watch some Youtube video's on spotting delamination, and RV inspections, Some are great, most are decent, and a few are insane, but after 3 or 4, you'll see patterns develop and be on the right track.
You can also hire someone to do an inspection for you, mobile service techs can be a great help on that.