When opening the vehicle for the first time, take a deep breath and see if you smell a musty or moldy odor. Look under the dashboard to see if there are any brittle wires, mud, or grit in any crevices. Also, check for condensation or water lines behind the instrument panel and gages.
Check the trunk area and look under the carpet or around the spare tire for any evidence of odors, standing water, mud, or salt residue.
Look at the carpet, make sure it matches throughout the vehicle. Has it been replaced or recently shampooed? Look under the carpet for any salt or water stains from evaporated water.
Check for mud, grit, water stains, salt residue, or rust on screws in consoles, change holders, and the glove box. Anywhere these items would not be normally found unless the vehicle was previously underwater.
Inspect for rust or corrosion on the inside of the vehicle on any metal areas most likely under the carpet and where the carpet meets the dashboard. Check small crevices on the dashboard for salt residue or stains. Inspect the door panels, upholstery, and door panels for any fading, water lines, waves, peeling, or odor.