Sensible advice above.
You want to find one with the right service history. Needs to have been looked after properly and of course don't forget the cambelt! 20V cars cost at least £600 from a specialist (and don't go to a Fiat dealer unless you've about £1500 burning a hole in your pocket!). Every 5 years or 36000 miles without exception - the owner doesn't understand the car if he/she tries to convince you it's 8 years or 76k (per the handbook)!!
These are also known for head gasket problems so check for overheating & water in the oil. Turbos suffer from engine oil leaks, and non-turbos from gearbox oil leaks (rarely the other way round), so keep an eye on the engine oil in a turbo.
They should come with a red/burgundy "master" key to reset the immobiliser rolling code if it all goes wrong. Rarely needed but can cost up to £500 to sort it out, so a good bargaining point if the car doesn't have it!
Of course loads have been thrashed & crashed, so you need to be happy yours is a good one. They are out there, but getting hard to find. I'd pay more for the right car - pay £2500 instead of £1500 and you'll probably save a fortune in the long run.
Good luck, Gavin.