Second hand phones can be very disturbing, I've also been a victim of such, in my own case, it was my brother that sold to me with full assurance that everything is good.
With trust I purchased the phone but guess what?
After some months of constantly repairing it, I lifted the phone and broke it into pieces with great anger boiling in my heart.
To me that is, was and will forever be the last time I would purchase such phone even if the person selling wants the money for operation.