2004 Audi A4 1.8T Avant Quattro Wagon - 170k miles coolant leak

[200q 20v]

Looking at seller's car. Seems like from the front of the engine.
Water pump? I am trying to find out when it was replaced. Owner
recently added Stop Leak and it appear to cure it, at least for now. I
never used it don't know if stop leak can case some damage in other
parts of the cooling system. Does anyone experienced anything like
this? Should this car be avoided? I know 5 cyl 20v runs 300k and more
with proper care, never had experience with 4 cyl 20v 1.8T, need
advice. Thanks.