The desktop CnC is a strange market. While it is possible to pick up a name brand 3D printer for less then 300$. A Dremel CnC would set you back 1k$ or so. I heard that the Chinese machines are quite nice and cheaper ones are priced similarly to a 3D printer, however I am yet to see a Chinese machine with a smaller then a 12"x12" cutting area. If you are to call these machines "table-top" you must have a very large table indeed.

If you are opting to build a CnC machine, it is tempting to follow one of those instructables which tells you to tear apart unsuspecting scanners and printers to salvage the moving components. I have never had good luck with this approach. Scanners and printers are generally built cheap. I never scavenged linear bearing, and the ones which did not use a belt used a threaded rod, instead of a lead screw. If you have a little bit of a budget (<40\$ per linear stage) going with the Chinese vendor becomes quite attractive. With a nice selection of all sorts of CnC related hardware from spindles to threaded rods. Be careful with shipping, since it can be far more then the cost of the item. If you are able to get all your items from a single supplier, it may be possible to negotiate bulk shipping. I imagine that being able to communicate in Mandarin would help quite a bit.