A Visa Check Card works just as well if you're in the US (or elsewhere they're available)--many banks offer them even with free checking accounts. That's what I use myself (glad to be credit card free). So long as your credit isn't horrible you should have no problem getting one, there's not really any requirement since it's a debit card.
I'm not even 18 and I have one as well. They work and are easy to get. And while Visa isn't as worldwide as people think (I'd have better luck here in Germany had I had a MasterCard), the web accepts Visa and that's good enough for many things.