My daughters and I all have the 4s's and service through Ting (which is a pay-as-you-go company). I bought the phones over a year ago outright for about $100 each. Since then, our monthly bill has never exceeded $45 for all 3 phones. And that's with calling/texting/data. I do limit my daughters' phones to 500 mb of data per month, but they usually don't come close to that. And they call/text a LOT, lol. We've also never had problems yet with the 4s not being able to run programs. We all have the latest iOS, and dd's have never mentioned not being able to download/play a game they wanted to. So, I say for it and get her the iPhone 4s, 
