Both AT&T and T-Mobile are now offering the iPhone 5C (on pre-order as of September 13) for $0 down-payment. This offer is for the 16GB version only and it carries with it a $22 monthly payment for 2 years.
Calculating this leads to the iPhone 5C 16GB costing you $528 which is about $20 less than the $549 price of iPhone 5C unlocked.
Carriers offer discounts of this type to get on the bandwagon when a new product releases. This is more pronounced during the launch of a new iPhone. This time, T-Mobile and AT&T subscribers will be the first to get their iPhone 5Cs for a zero down.
Along the same lines, iPhone 5S 16GB gets a $99 down-payment too but there aren't any discounts by the time you finish the monthly payments. The unlocked iPhone will still end up costing you about $649.00. Also, the 32GB iPhone 5C will cost you $22.91/month for 24 months along with a $99 down-payment – ending up in $649.00
The iPhone 5C 16GB is being sold by Apple for $99 (on-contract). The iPhone 5S 16GB is sold for $199 (on-contract). The smartphones are available on all four carriers: AT&T, Verizon, Sprint and T-Mobile.
You'll have to subscribe to AT&T Next in order to avail of the zero-down offer for iPhone 5C. The same rule applies for T-Mobile where you have to pick one of their plans to be eligible to pick the $0 iPhone 5C 16GB.
While pre-orders for iPhone 5C have started, the expected shipping is September 20th and later. The iPhone 5S too launches on the same day.
Read our iPhone 5S vs. iPhone 5C vs. iPhone 5 comparison here. Also, if you're stuck between choosing iPhone 5C 32GB and iPhone 5S 16GB (because both cost the same on-contract), here's something to think about.