I'm visiting the states for a few weeks, and found some good looking offers on Craigslist. I'm about to buy a i5 2.4 Ghz Macbook Pro from someone for $1650. When I look over it, I'm thinking of calling Apple to give them the serial number to check if it was stolen or something does that make sense? The seller also doesn't want to give me the receipt, but I can look at it. Is that normal, or something I should be suspicious about? Wouldn't I need the receipt for any future repairs under the warranty, or is a copy enough?