Water intrusion is the enemy of campers.
ANY (and I mean ANY) water damage or discoloration, including mold, is cause to keep looking. Sometimes even "free" is too expensive.
Also look for dampness in any compartments. Looking at used equipment after a rain is best if possible.
Also look for unusual wear indications on the tires.
Lou, Laura, & Freya the wonder dog
2008 GMC Sierra 3000HD Crewcab SB Allison Duramax
2019 Flagstaff 8529FLS - Pullrite 3300
HAM CALLSIGN - KC3FFW