If your new to nitro, buy one thats brand new, that way your not buying something with problems you know nothing about.
You WILL spend 70% of the time fixing and adjusting settings / putting in new parts / etc etc
So if you dont want to, simple answer is, dont buy a nitro !
I've had a Savage 25, Revo 2.5 and a Hyper 7, and i can 100% say that the hyper has been by far the easiest to work on, the most reliable, and the most fun. So my advice is... buy one of those, you wont be dissapointed.