I'm not sure where you are in the world but with the history of hurricanes and storm surge floods in highly populated areas of the USA, there is high probability you have a car that was submerged or partially submerged in salt water. These flood cars can get moved from state to other states that have easier title laws that allow salvage or rebuilt titles to get cleaned and appear good. You also can't trust carfax and that is all assuming that the car was insured. If no claim was ever made, the title would be clean.
Salt water is a mild acid that even when submerged for a short time can attach seals, electrical wiring, connectors and the connector seals. If the water got into the car where the electrical connectors are not sealed or internal control modules that are not sealed come in contact, it is a long term electrical nightmare because the issues will be intermittent, hard to diagnose, and all kinds of weird things can happen.
Anytime you come across unnatural corrosion for the geographical area or mileage or rust in weird areas of the car (seat brackets, seat belt mounts, underdash structure). The hardest part is identifying vehicles that are in the rust belt but came from a northern flood like Hurricane Sandy.