Don't use Traktor, if you want turntable + laptop software I would suggest he use
Serato Scratch Live (I own and have used both for years). The SL1 interface offers all he really needs, and is about the same price (SL3 is a bit easier to 'preview' with due to the aux output but is more costly.) Any Mac or PC laptop with decent power will work for just mixing though the pricier SL-3 requires usb2. For just straight 'mixing' like a techno dj even a 1.6Ghz celeron (p4 era on) will do the job, but for doing hiphop/battle/dmc style 'scratching' (requiring fast cue work and loading songs quickly etc) and/or using any of the looping/video out you'll want something from the last 3-5 years.
For turntables I just recommend a good used set of Technics 1200's (mk2 are fine and mk3d, mk4 & mk5 are all since on the market.) Pawn shops in Vegas might be pricey, but I can usually find a set of mk2's for $250-300 (mk5's new from guitar center are under $500) and these will be saleable for not too far off that mark if he bores of them (which will not be the case with any gemini/numark decks.)
Needles for 1200's can be pricey, if he's capable of caring for gear though I think Ortofon needles are the best investment-- nightclub or Dj Pro(blues) in the 'S' or spherical model ('E' or eliptical wears vinyl more and is much shorter lasting.) All of the Shure 'scratch' needles (like the whitelabels on up) are so flexible an inexperienced Dj will chew through needles like crazy, meaning you'll wind up spending more than you would have on Ortofons to begin with. Trackmasters and other numark offerings (as well as technics) are serviceable and probably almost as sturdy as the ortofons. The one downside to the Ortofon is the 'concorde' type stylus (which I prefer) has narrower contacts in the rear which can cause poorer contact if the needles are constantly removed, though this is actually an issue for any non-technics needle: all vary in spacing thanks to the patent from Technics on their spacing. So the best solution is the cartridge that mounts into a headshell, and use the stock technics headshells if you can find them. The downside is learning how to mount those and maintain them (the concordes are simple, just install them and don't do anything but swap needle tips and you'll be fine.)
However before even going there, what aspect of the Dj culture is it that appeals to him? Battle/DMC? House/techno style mixing? Not having played any of the new dj games I'm guessing they do more of the former?
