Be ready to invest some money into it, there are going to be things that need to be replaced, afterall it's a 30 year old bike.
Things I would look for:
condition of the plastic, is it missing tabs, cracked, paint condition.
Bottom of the trunk will crack out on some bikes.
Paint condition.
Age of tires, sure they may only have a few miles on them, but how old are they.
Things I would plan to go over before I ride it:
Brakes, including a caliper and master rebuild.
All wiring connectors taken apart and cleaned and then coated with fluidfilm.
Check and lube the steering head.
Change oil, including the forks.
Lube all points on the swing arm and remove the rear tire for complete service.