If you haven’t already, I suggest checking out the “Digital DJing Fast” course. It will give you a leg up, especially on the EQ and other technical points of DJing.
As to where to get current generation music – assuming you wish to do so on the cheap, I recommend checking out Soundcloud. There is a CRAZY amount of really good music posted there for free download (not all of it is freely downloadable, so there is some “crate” sorting involved). There’s even more NOT good music posted there, but… sorting through music is really what our jobs are all about. I get almost all of my music from Soundcloud (and its siblings like HearThis.at)… I’d say 95% of my music collection is free (legally), and I paid for the other 5%. I’m a bit of a cheapskate.
Alternatively, iTunes is a popular way to get the mainstream top 40 stuff… Beatport, Juno, Traxsource are all popular spots for getting dance tracks.
If this is something that you expect you might be doing fairly often, you could consider a DJ pool – there are several to pick from (I don’t use them, so can’t recommend any one in particular)… and you should be able to find one that will give you current new dance tracks.