Selling broken iphone 4 att unlocked 16gb

Bought an iphone 4 from my sister it had a cracked screen so i was just going to fix it but it didn't effect the phone at all so i just left as is and used it for awhile. well one day it started to be hard to get it to wake up but it still worked fine no signs of water damage or brute force to it. couple days late it won't turn on at all. Just a black screen, itunes will only recongize it while in recovery mode. still just a black screen. Gazell.com will pay $50 for it just seeing if anyone on here is good with fixing phones and wants to buy it to try and fix or use for parts. add my skype or post here

 

Is it a Verizon or att phone?

 

willing to buy it for 80 but i don't get what you mean", itunes will only recongize it while in recovery mode"

Does it have a error code?
can i see a picture of the iTunes?