Pive vs Active Speakers and some good recommendations for a mobile DJ.?

I am looking for a pro audio setup that doesn't cost a fortune. I am very unfamiliar with it all, but I have read that having a sub woofer improves the sound greatly. I am looking at Mackie TH12A active speakers, but then I would have to look at a sub woofer that is powered itself? I have also heard that you can go pive speakers and then a powered sub woofer and it will power both the woofer and the sat speakers? I think i would rather have active than have to buy a amp to power everything. So my question is what are some good setups that are not very costly but also are not crap, and some help on explaining the whole deal with active speakers and subs vs pive. I am looking to start a mobile DJ business. Thanks!