A car that old you'll have all on to find mint without paying the earth, but tatty is tatty out there and there are some right sheds. Check the boot the edges of it, a common trap for water and these panels were not from VW and are the places more likely to rust, slam panel at the front is another, check the rim underneath the roof where it meets the body, start pulling rust off from here walk away. Check the window frame at the back these rust very quickly if your planning on replacing the roof you would need to budget this is.
spec is pretty much the same as a gti except there is no mfa and its carb fed, later 1990 cabs gained electrics and updated door cards allowing bigger speakers. fusebox, water can get onto this, check the contacts as the fuel pump relay can fail and youll find yourself on the roadside, most components are mk2 and you can pick them up for peanuts down the scrappy.
Gearbox can leak as the seals tend to degrade. if you know the faults you can bargain a fair bit, some people get rid of their cabs at the time the problems start i bought using my eyes and never checked anything it cost a grand to put right.
And bare in mind they rattle, dashboard fittings are not amazing and over 90mph and the roof sounds like yer grandmas beating down on it with a brolly. Thats half the fun of them.