Pre-buy.
I didn't see the 421 mentioned in the link but I'm sure it's likely included.
Cape air had a problem with a couple of their 402C's.
Mental note, it wasn't just the wet wing. The earlier models were a problem too.
I also remember several AD's concerning prop hubs cracking and exhaust leaks.
They were 50hour reoccuring. Since the exhaust goes right by the ring spar, a leak could mean a bad day.
(ask me how I know)