Karaoke Question

From my band days, I have what is essentially a brand-new PA system sitting in my storage space. I've used it only a handful of times for gigs and we use it a couple times every summer when we have big parties. I hate to have this thing sitting around gathering dust, especially since it's much better than most of the PA systems I see in use at clubs. So here's what I'm thinking...

I could go to Sam Ash or Manny's or something and buy a Karaoke machine, along with a few discs of popular karaoke tunes. Maybe I could take a Saturday night gig at a local bar.

Anyone know anything about this? My questions are:

1) How much does a good Karaoke machine cost? 2) How many discs do you need to start with in order to have a good selection of tunes for people in the bar? 3) What do the discs cost? 4) How often do you buy a new disc to keep pace with the new tunes coming out?