Listen for engine noises from the cambelt area, the accessory belt idler bearing has a tendency to get very noisey as the idler is exposed to water ingess from the front bumper.
Also check for oil leaks, I dont mean silly little leak more like oil dripping when engine is running from the back of the cyclinder head cambelt side.
Have not had to much trouble with mk1 172s they are pretty good, check the servicable item like tyres, pads, discs all that sort of thing.