Draw backs of buying used CNC equipment?
Almost no support for your machine especially if your a small shop that never buys new equipment or is far distances from distributers.
Inherit someone else's problems
If the builder does not make any money on it, then they will most likely not give you the support you may want. The fact is, the greater the potential for new sales, the better the service and tech support.
Support may also be more difficult from a knowledge stand point if the dealer just took on the machine tool line within the last couple of years.
Think of it like buying a used car. You always find yourself a good mechanic to take a look at it if possible first. Even then you may miss some things that can cost you lots of money down the road.
Certain types of machines can be easier or harder to find parts depending on the model and the control type.
Consider the controls, buy the most well known controls like Fanuc. Why? parts are readily available. Almost every service person has worked with Fanuc controls. They also have many benefits for your operators, programmers and other personnel who are familiar with the controls. You do not have to do any additional training. It saves troubleshooting and repair time.
Some builders have gone out of business or will be going out of business shortly from a sinking machine tool market and less machine tool upgrades.