Swing arm and related bearings are normally neglected and get dry. Once the grease is gone, the bearing pin destroys the bearing and wears into the aluminum. This is expecially common on the bottom shock bearing. When you get the bike, disassemble the rearend and clean/grease all bearings. There are now companies that make swingarm rebuild kits that will save you a lot of money over stock parts.
Also check the swingarm rub guard on the bottom. This get worn out by the chain, and since it is below eye level, gets missed.
Have fun with your new toy.
Rick