I would think it would be just like with cars from questionable areas. They may or may not have been declared salvage, may have had the title "scrubbed" to show clean, or may have been privately dried out and not show anything odd. All bets are off after and event like this, but the vehicles will be delayed by several years in many cases, which makes them low miles for the year, and probably looking very good to the eye.
Carfax for sure on any used vehicle to see if it has ever been in a flooded area during an episode, even if Carfax is clean, if it was in the area the vehicle needs a very thorough water damage inspection.
We see the southern cars here in Minnesota all the time, as all the locals like the idea of a history of no salty roads, but with that benefit comes the need for more diligence in relation to the bad things that can happen in the south.
Salt water flooding is particularly bad, and there is nearly no chance that they can be dried out fast and well enough not to have electrical issues. Fresh water flooding is better, but I would still not want one.
I was just on Craiglist today looking at stuff, and it seems like 1/3 of the vehicles show a salvage title, and many more than that being shown without plates on them, so very likely from somewhere else.
Bottom line, be very, very, very, very, careful and don't hesitate to spend some money on a very thorough inspection. If the seller balks at that, time to walk. Very common here to insist on an inspection with the adder that if it passes clean, you pay for it, but if it comes up with any of a list of severe undeclared items, the seller pays for it. Good sellers are fine with that, as long as the list doesn't include minimal items, bad sellers will want nothing to do with it, and usually offer a lower price instead. It is then time to run.
