That looks like 50 taper machine? Do you need one that big? If you plan on cnc'ing it, then its a better idea to get a older cnc mill that way it already has ballscrews motor mounts a nice lube system a lot of wires, control boxes nice and way covers. The first mill I cnc'd is a old bridgeport M head machine I made it two axis after thinking for a long time how to but a motor on the quill I gave up and bought this:
http://www.cnczone.com/forums/showthread.php?t=34843 (BP BTC II Retro)
If you buy a machine and the screws have a lot backlash you can get them reloaded and get new support bearings. After doing a convertion on a non cnc machine I would not do another one, for a next machine I will buy a old enclosed VMC clean it up put new controlls in it. I also have a Cincinnati #3 mill, here is a pic of it with my little bro.