I bought my first truck off the money I earned through gathering scrap metal on rough-ins when I was a kid. My dad started letting me go as a clean-up man when I was 8 or so. I'd get all the scrap copper, wire, etc that I could find and haul it home. I eventually filled up one of those large, circular watering troughs for live stock. Cashed it in at Lake June Scrap Metal on my 16th birthday and came away with a little over a grand. Enough to buy my first pick-up!
If you do change outs its worth the time to strip it down. I did a 2.5 ton split few months ago, stripped coils, line set and metal and got over 200 bucks not bad for 20 min. of work. I was kinda shocked it was that much.