It is possible to purchase an iPhone and still be able to use it on cell phone provider networks. You just need to know how to unlock iPhone 4s sprint will not keep you from using it on their network. It is an easy and legal process. The first thing you will need to do is to jailbreak the iPhone.
To jailbreak the phone you will need to download special jailbreaking software. This is important to the process because it will allow you to use third-party software to unlock the phone. Redsnow is a free program that is free to download and it can be run using the desktop. After you have selected your jailbreak software and downloaded it, connect the iPhone to the computer with the USB cable. Now open the jailbreak software and carefully follow the simple steps to jailbreak the phone.
Once the phone is jailbroken, you will see a new icon on the home screen that is named, Cydia. This is just an app store that is run by a provider other than Apple. You can still use the App store, this is just an alternative. Open Cydia and search for redsnow or ultrasnow. Whichever one comes up in the search results click on it and then click install. The phone is now unlocked. Turn the phone off and use a pin to open the SIM tray. Remove the SIM card and replace it with the Sprint SIM card. Turn the phone on and wait for it to identify that it is now using the Sprint network.