[suicideneil]

Depends how used they are and who used them. More established members on forums with good feedback are pretty reliable, and you can guage the condition of the motor/ esc by looking at the photos- if they have nothing to hide the pics will be clear and numerous, with a good description of how its been used.

I would point you to LincPimp's motor sale thread in the general section for a good example of a trust worty seller.