I actually own one, one main thing is that the top plastic palm rest part might crack at the lower right side. Like if you are a righty and pick your laptop up with your right hand, with the fingers under the laptop and the thumb on top of the palm rest, at the edges the plastic is weak and might crack.
The keyboard, the plastic between the keys, gets bowed over time. Also the bottom case. Make sure it's flush with the battery.
Just act like you know what you are talking about and if there's any damage just say it's damaged and cut the price down more.
Make sure the screen is bright enough, it might be getting old and stuff.
Click the apple>About this Mac>More Info>look on the Power tab> half way down it'll say battery:
Charge Information:
Charge remaining (mAh): 4539
Fully charged: No
Charging: Yes
Full charge capacity (mAh): 4641
Health Information:
Cycle count: 126
Condition: Normal
That's mine, I guess it's okay im not too sure. expect maby 300 cycles for a 2 year old computer. Maby more. But if the two numbers are vastly different then the battery is OLD and used a lot.
