It's surely a fun hobby, but not a financially sound one at all :) Especially not when you're going the vinyl route as I did, though it is the coolest!
I did this when I was in college. Proper equipment is expensive, and you don't want cheap stuff as it will have a negative effect on your experience. Resell value is decent, though (on the hardware, not on the records if they're not rare).
You could try some DJ software first to see whether you like it before investing in hardware. I create some mix CD's using MixMeister Studio once in a while, though this isn't strictly DJ'ing as you don't mix in real time (and beatmatching etc. is done for you).