One thing that hasn't been mentioned, do a title search.
+1
An old lien can be a nightmare. From time to time banks have their baby loan department people go back into old records, particularly of banks they've acquired in mergers, to see if they can find any money. When they find an unreleased airplane lien, the kid thinks he's found gold. It can be a huge pain to deal with them - and you may have to pay off the lien to get a clean title on your airplane.
An released lien is, IMHO, a deal killer when you're looking to buy an airplane.
