Where's the car? If it's in TN, when looking at the car, get
down on the ground and _look_ at the underside. Yes, you can
see most of it just by looking underneath it, and the likely
rot spots are under the front driver's/passenger seats, and
just in front of the rear bumper. Also, check for wet carpets -
my wagon rusted from the inside out due to water leakage into the
interior. It has no other rust underneath, despite spending
most of its life in Ohio, Long Island, and the mountains of
California. If the carpets are wet, ask the owner if you can
check underneath them for rusting. Pulling off the plastic trim
pieces on the doorsills will allow you to pull up the carpets
and underlying foam to some extent and shine a flashlight underneath.
.
If you can't look at the car, then ask the owner to put it up on a
lift, take digital photos of the underside and send them to you.
If the car ends up being rusty once you go to pick it up, kvetch
very vocally!
.
Lastly, don't worry too much. My parents had a 1982 BMW from '82
until 1997, when it got totalled by someone driving _across_ the
NJ Turnpike. The car only had a few tiny surface rust spots at
the time, and had spent all of its life in salty, snowy New Jersey.
.
Good luck,
-b.