I think that if you want to do some developing with this phone you better get some old flagship phone that have android 5.0 like Samsung Note 3 or LG G3 for example rather then a new cheap low grade, the reason for that is that as a developer you would like your phone to have as many sensors as possible so you can check different features of what ever your application you trying to make, like using NFC, IR, etc., in cheap phones you would not find this kind of sensors and it may limit your app development testing. you will probably get those old flagship phones at the same price as the cheap new ones or even less.