Figure out how many kegs you want to dispense / hold first, and then find a chest freezer big enough for that. I got a new one. used are easy to find on craigslist, but who knows how long they'll last.
You don't necessarily need a temp controller on it, though the STC isn't expensive. There's a way to adjust the thermostat to get up to fridge temps on most chest freezers. You have to take the thermostat out and find the course adjustment screw. I did that for a year and it worked fine. There's a thread somewhere on HBT that shows how.
Get a keg / CO2 tank / regulator / disconnects / picnic tap. You can find a kit with all of those things for about $200:
http://www.homebrewing.org/5-Gallon-Ball-Lock-Keg-System-w-Picnic-Tap-USED-Keg-1_p_69.html
For now, just stick the keg and tank in the freezer and dispense with the picnic tap, no need to build a collar or get nice faucets right away. Eventually, if you want you can go that route. You'll likely want a longer bev line on the picnic tap than what the kit comes with, but that stuff is cheap.