Quoted By:
You can score some deals, but look for private sellers. Commercial sellers are more likely to sell junk in my experience.
But be careful, buying in person is better than mail order. If it's too far away, take a good look at the provided pictures.
Is there a perspective missing? Is the seller trying to hide something? People that have no idea about what they're selling are where you'll get the best deals, obviously. But they're also less likely to notice faults with the lens.