For $500 hes got several option............I think the Rane tt-52 is around that price.there's also the Numark SM series with the optical fader, i belive the SM-2 runs in that price range.....in my opinion these are the best choices for scratching specially that SM-2, he will not ware that fader out any tme soon.
For, say, $50-60 bucks more he could get the same turntables but with a better mixer, because frankly, the little stanton mixer that comes with the skratch pack seriously sucks donkey balls.