I'm of the opinion nothing is above ones ability. If you have the gonads to run a machine tool, nothing mechanicals is beyond your ability.
It may be beyond your desire, might not fit your time frame, it might not be economically feasible. But given the correct motivation, you can do, re-do, or undo anything. Unless some have a super power I am not aware of, they cant do nothing you cant.
That being said there are only two things that you need to start with. First being amount of money in your pocket and the second being the amount of work you want to do. New or used, these are going to set the tone for what you look at. Out side of size limits, everything else can be worked out.
I have done a ton of looking into this cost wise. Best bang for the buck that I have found off the shelf was the pm45. Though I heard they wont carry them any more.
Most others cost so much I have a hard time not looking at used cnc or retro fit/conversion.