Just off the top of my head, some I have experienced, some I have read about and hope not to experience:
Check the cooling system thoroughly to see if it has been kept up. The 4.7 liter does not deal with heat well, and are known for one redline to cause a leaking head gasket or warped head. The radiators are a definite weak point in these, they are aluminum with plastic end caps and split at the seam where the metal and plastic meet. The coolant must be kept fresh or the radiators also clog up.
If the truck has an LSD, the factory retaining clips for the clutch packs break off and float around in the diff until they are either caught by the magnet or wreak havoc on the gear set. The pinion seal is also prone to leaks.
Front wheel bearings are subpar from the factory.
The blend door hinges in the HVAC box are known to strip causing air to either come out of the wrong vents or none at all, and the heat or air conditioning to not transfer correctly.
This is all I can think of at the moment. Most of these problems happen pretty early on and are likely already dealt with being an 02. That is a nice truck you are looking at, and it looks like the PO took pretty good care of it. I hope the truck checks out and the deal goes through for you.