Niree_22, upgrading to a new equipment may require a down payment, that and all the information concerning the device pricing wll be provided by the agent assisting you with your upgrade. You can also view your pricing once you log into Sprint.com and place your order in the 'cart'.
If you have any other questions or concerns, please let me know.
After upgrading to a new iPhone on the Sprint Flex, this will include annual upgrades at no additional cost. You can learn more about Sprint Flex @ http://sprint.co/2uV2oP8