Don't be rude. Seriously. Don't low-ball them, they will take you for a kid and decide not to sell to you. Do your research and know how much the model is worth/currently going for. Offer that amount - if there is damage, rubs, scratches, etc. point it out nicely and adjust your offer accordingly. If they decline, you can always ask what the lowest amount they'd take is. If their lowest is still unfair or too high, decline and buy from someone else who actually wants to make a sale. My view: it's better to sell for a bit lower than expected than not make a sale at all. If the seller is EVER rude or condescending, just walk away. I look young, event though I am a legal adult and have had sellers treat me as if I know nothing. Walk away, do not buy ANYTHING from them. No need to support the rotten apples.