I bought a 2014 4Runner from Western PA and I live in Northeast, OH (in snowbelt area). We have a long winter with lots of salt. I expect rust and going to try really hard in my truck's ownership to maintain it as best as I can. I think the original owner didn't really take care of the undercarriage and so far I am only noticing rust on frame joints and nut heads. The skid plate is also pretty rusty too but that doesn't bother me.
For this winter, I am borrowing a friend's Fluid Film applicator and going to apply some of that underneath the car. I already have my truck fully waxed in preparation for the winter.
I would take a look underneath and if you see anything that worries you a great deal, take a pass on it. Coming from NC, you should probably don't see much salt so I am sure you would prefer a rust free truck, especially since it's used already.