How can i find out if its stolen?

I met a guy at college selling his xbox 360 for $100 bucks he says he is the 2nd owner and nvr got on live so he didn't register it in his name... I want to buy it off it but I'm afraid its stolen bc of the price...I heard that if buy a stolen box and get on live it locks the system up and tracks to where you are (I dont want to get in trouble for having a stolen xbox 360 when i bought it).... is there a way i can check like the serial number somewhere to see if its stolen...