I don't see the harm in going to visit the car. As long as you go with a level head and road test the car etc. To be honest it sounds like it's had some money thrown at it. Motec, ap racing brakes etc so could be well built.
Make him an offer that allows you 3k to sort its issues. New disks & pads (check when there), clutch, ALL fluids changed, new tires as they will have flat spots, new battery, boost leak investigation, injectors out and cleaned, new plugs. After that its fingers crossed.
You need to drive it hard on the road test, change gear from 2nd to 3rd at really high rpm to check that synchro as that's and expensive fix.
The owner obviously doesn't have a clue what about the car which can mean great car for cheap because he took it off the road for a simple issue he didn't know how to sort or money pit. (I'm going with option 2).
Remember though that owning a single turbo is not like owning a BPU TT - it's a fuck load more fun but you need to understand how it works to keep it running. If your not bothered about owning a single then don't buy one.