Can I buy an iPhone without a SIM card?

I'm buying an iPhone 4s from Craigslist. It is supposedly in good working condition, but has no SIM card. Is this a scam, or is it simple enough (and cheap) to get a new SIM card? Would I be able to do this at a Verizon store? I leave for vacation on Sunday and would like to have it working by then.

More specific please

Well, it's not the best place to buy an iPhone but, it is possible to buy a phone with our a SIM card, you would just have to purchase one. It's not a scam unless there's problems with the phone. Just make sure to ask them if there were any problems with it. Make sure it is with your carrier too ( Verizon AT&T tmobile etc.) if you we're with Verizon and he gave you a t mobile phone. It wouldn't work even if I doesn't have a SIM card trust me I've tried