you may find a hand mill for 500, used. but def not a cnc. heck, the stepper motors alone cost near that. much less the whole machine.
ive got availability to alot of metal working tools, and a medium amount of welding and other experiences. and i kind of fell on my face when i was getting ready to make one. the problem is definately experience, so if you dont know what couplers, stepper motors, g-code, collets, what kind of end mills for different feed rates and materials, ect. are, then i hate to say it but your about 1+ years of researching before you lay your hands on making one. sorry.
easiest and closest thing to do would be this.... make a copy carver. guitar frenzy had a pic of one when he had his 'make a strat' tutorial. i would build one of those. not to hard but still a good bit of work. THEN, learn a little bit of CAD, and take a 2-D autocad prs, lp, strat body template and convert it to 3d, so you have your carved top dimensions. THEN take them to a machine shop (that will even think about doing wood) and get them to mill them out of solid maple or a good reliable wood using your 3d cad file you made.
so then you have some 3d templates of different bodies you can use on your copy carver.
sounds like a plan to me. seriously dont waste your money+time on trying to make a cnc to start off with.