^yes, off base is WAAAY better, move off if you can.
and remember you wont be the first one to buy a car and live off base. Pass & ID and the housing office can answer all your questions. $5K should be plenty to get you something decent when its all said and done.
Rob at EAW can get you anything you want, including stuff off YAJ.
local misawa car forum:
GaijinDrift
most of us have moved away but theres decades of misawa related car knowledge there, just ask