Make sure it runs under power. Check air filters! This is a good indicator of the type of PM the machine has received. Turret works? Chuck works? Flood coolant works? Spindle sounds OK and will shift gears? Is the CRT clear? Tail stock work? Take a test cut. Make sure turret is on center and it does not cut a taper. Check Hydraulic tanks (yes, there are 2) for color of oil, sediment, etc.
Does he have all the books? And back up software?
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)