Looking to purchase a PU, any specific places to check for rust?

[Grandpa's Aurora]

I'm in the Atlanta Georgia area. I'm shopping currently for my first pickup and did some searches but did not come across any that say what to check on the body i.e. places that are prone to rust.
There is a 1977 long bed that seems pretty reasonable but the ad says the bed is rusted. Before driving to look at it can anyone tell me where else to look for rust? I know to look at the frame, quarter panels, bottom of doors etc. But I've never had a pickup so are there specific area's that I should check?
If you can point me to a prior post about what to look for that would be great too.

Thank you..

[TotallyScrewed]

cab corners, wheel wells, any place dirt cakes on the truck... stuff like that. and the bed floor as well.

hope that helps.