iPhone 3GS No Service - Cause?

[iamamac]

Hi guys, I'm about to buy an iPhone from a seller on eBay.
He describes it as a working DEVICE except for the telephone part. Basically it says the handset its locked and cannot be used as a phone, giving the "No Service" error in the left corner, he also said he believes (he didn't tested it) that it works with foreign SIM cards. Now, I'm asking you, what can be the cause of this? Worst and best case? Should I even buy this phone? Many thanks to all!

 

[nathania]

Don't buy it unless you're absolutely sure. Aren't there other iPhones on ebay? Plus, you can get the 3GS for $99 now, so why risk it on ebay?

 

[iamamac]

Don't buy it unless you're absolutely sure. Aren't there other iPhones on ebay? Plus, you can get the 3GS for $99 now, so why risk it on ebay?

I already have an iPhone 3GS for myself, I'm not buying it for me, I'm buying it for a friend who doesn't have too much money and I gotta say this is a great deal. And besides I'm not even in the US right now, I wouldn't renew my AT&T anyway.
Assuming it's stolen or bricked, would it display the same message? Are there any specific signs of blocked IMEI that I should be aware of or it's just an unlocking done wrong? Thank you!