Apple is changing the way Americans can pay for their devices. Instead of requiring customers to buy an iPhone outright or commit to a traditional financing plan, Apple is introducing a new leasing option in the United States that could make upgrading to a new device more flexible — but also raises some interesting questions about ownership. The new program, called Apple Upgrade , allows eligible customers to get an iPhone through monthly lease payments. Rather than paying the full price of the device upfront, customers make monthly payments for a defined period and can then decide what they want to do when the lease ends. According to Apple, the program starts at $17.99 per month for eligible iPhones, although the actual monthly cost depends on the device and the customer's agreement. The biggest difference is simple: leasing a phone isn't the same as buying one. With a traditional purchase, once you've finished paying for the iPhone, it's yours. With a lease, you...