Another option for a cheap CNC machine would be to start with the Micro Mill
for Harbor Freight
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=47158It's on special right now for $259, and with a 10 or 15% coupon.....
If you can keep the cost of the mounts, motors, and drivers to around $250,
that might work
That gets you away from having to align rails, etc, and the mill should be
ok for making the motor mounts, esp if they are out of aluminum.
One downside is the work envelope of the xy table is fairly small.
Randy