If you want to run AOSP/etc you'll need to buy a used S4 with MDK (e.g. on swappa). They generally sell for a bit more than non-MDK ones, but I've seen them as low as $310-$335 recently. Lowest currently is $360 though. Basically, assuming your S4 is in mint/near-mint condition the price difference should be under $50 if you were to sell yours and buy one with MDK.
OK Google. Make Me a sandwich. How many times have you … more
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?