I disagree..
I wanted to start DJ-ing so what I did was I went on e-bay and bought a pair of Numark TT turntables, with a Numark amp for about $350. One of my boys let me borrow his Serato SL1 box Mon-Fri while he was in school and didn't need it for his gigs. It's a preatty crappy set up but it taught me the basics of beatmatching, dropping in tracks, taking them out, working the crossfader, scratching, etc. Granted you cant do as much on Numarks as you could on Technics MK5, its still a set up for a cheap price.
My mentality on the situation was this. If I bought cheap equipment and didn't really get into becoming a DJ too seriously, then I wouldnt feel guilty letting $350 worth of equipment sit in my garage unused. But if I spent $1000-$1500 on a good set up and didn't get into DJ-ing then I would be annoyed. The resale value on this type of equipment is good, but like any commodity a used item is still a used item..it is going to depreciate in value.
Now that I have been practicing and I know this is something I want to pursue I dont mind selling this set up for $100-$150 and putting it towards a good set up because I know that I WILL use that set up and the money I spend on good equipment wont go to waste.
Oh and P.S. don't get any of that DJ simulation shit that looks like a toy. Get the real deal get some turntables, mixer, and Serato (or Traktor if you want to use MIDI)
just my two cents..