first of all, you are about to buy one off the most beautyfull compact cars around.
are you going for the flappy peddles selespeed ? Or the manual gear box ( which would be mine pick)
there are not that many problems with the 147 except some issues with the original front wheel arms ( do not know the English name for it) but these arms are easy to replace by improved once and not expensive.
I always would go for one with a service manual and low milage and if possible warranty.
Which model are you going for ? First or face lift ?
If you want to know more? Just ask, I know alot of these cars;)
I have a club and 2 sites about these freaking alfa's
Alfa147club.nl & alfa-meetings.nl