No, there is not a policy that I know of. Disclosure is a good idea, tell your potential customer what you did. If there is a return policy, or not. State weather you can ship it and where. State your payment options. Good pics tell a story a 3" thick novel can't.. Take pics of you packing it and at the drop off, on the scale.
Note. Pack it like it's coming back to YOU not THEM.. That is the trick in packing..
The sale is only final if the customer receives what they pay for. What they received may not be what you shipped.. Pack it well.. If it moves in a box, it's WRONG.. :-)
Regards