Look for rust in every nook and cranny, particularly rust in the bulkhead and rust in the rear half of the chassis.
CHECK the MOT history on line, this will list all the old fails.
The lower half of the front door frames will be rotten and most older Land Rovers are plagued with third rate repairs by incompetent previous owners.
Avoid anything that has recently applied black gunge under-seal, the sole purpose of this is to hide the aforementioned rust and 5hit repairs.
Never believe a single thing a motor trader tells you and remember that there is no such thing as a bargain.
It is very easy to tart up a piece of 5hit banger with a bit of chequer plate and chunkey tyres, but remember that these are very old commercial vehicles that will have lead a hard life.