How much would you pay for a new iPhone 5s? How about free? Of course you would, and if you have an iPhone 4S in good condition to trade-in Radio Shack will give you Apple\u2019s latest iPhone for free. Well, there is a catch \u2013 there always is \u2013 but it\u2019s not all that odious unless you hate being committed to a carrier. To be eligible for the deal, you have to sign a two-year contract with AT&T, Sprint or Verizon. Since T-Mobile has gone contract free, its subscribers aren\u2019t eligible.\n\tIf you don\u2019t have a phone to trade, you can still get a discount . Radio Shack will sell the iPhone 5s to you for $99, $100 less than Apple's price for the 16GB model \u2013 with a contract. Neither the 32GB nor the 64GB models are on sale, according to a Radio Shack spokesman.\n\tRadio Shack has not said if the offer has an expiration date, but like that carton of milk in the fridge it probably does. So if you like this deal don't wait too long.\n\tSuppose you don\u2019t want to mess with a contract, but still would like to save some money when you trade up. One thing you can with that iPhone 4s is to sell it. At Gazelle.com, for instance, you can get $130 for the 16GB version of the 4s, provided it has no cracks on the screen or body, makes calls, and has no major scratches or scuffs. Even if it\u2019s pretty beat up, you\u2019ll still get $40 from Gazelle.\n\tBest Buy has an almost identical deal \u2013 $131 for the same model in good condition.\n\tRadio Shack has been troubled so long I haven\u2019t paid much attention to it. But it appears that the company is trying to revive its fortunes, so it could be that the iPhone offer is a taste of good bargains to come.\n\tDon\u2019t forget to wipe your iPhone clean of data if you trade it in. Even if the store you sell it to says it will take of that, don\u2019t count on it. Your personal data is too precious too risk.