minimum you need:
1 C02 cylinder
1 Manifold (plan early here with the amount of lines you think you'll need and get adjustable check valves for each line)
1 Gas line with disconnects
1 Corny keg (you choose Pin-lock or Ball-lock)
1 Beverage line with disconnects (get the right beverage line from the start. Vinyl tubing gives off a plastic taste to the beer that sits in the lines for more than 15 minutes or so. I have Accuflex Bev-Seal Ultra 3/16'' lines and they are the best. I've left beer in the lines for 2 weeks with not a single bit of plastic flavor coming through. With some work you can fit them over 1/4'' barbs too. Accuflex Bev-Seal Ultra Barrier Tubing 3/16" ID - 100ft - FREE SHIPPING - Birdman Brewing Company Store
I use 20 ft. per tap at about 14 psi and the flow is perfect.
1 Tap and however you want to set it up. I use Perlick SS faucets. They are awesome, but expensive.
Price wise, i don't really know, i haven't checked prices lately. I'm sure it won't be too bad though. Really depends where you get everything, if you get it used, etc.