With much fanfare and hullaballoo, T-Mobile USA CEO John Legere announced that the company will finally offer Apple's smartphone. The iPhone 5 goes on sale from T-Mobile April 12, but customers can sign up starting April 5. T-Mobile is advertising the iPhone 5 for $99, but that's not necessarily what you'll pay. The $99 is actually a down payment on the iPhone 5. Thereafter, T-Mobile's iPhone 5 customers will make monthly payments of $20 for 24 months until the device is paid off. Between the down payment and the monthly installments, the total amounts to $580 -- that's about $70 less than the iPhone 5's raw $649 selling price. As soon as the iPhone 5 is paid off, you'll own the device, whether or not you stick with T-Mobile USA. Even better, once you own the device, T-Mobile USA will unlock it so it can be used on competing networks. (Yes, new phones will be locked to T-Mobile's network.) The beauty of T-Mobile's new model is that there are no cont