If youtube had been around at the time, and Minnesota Moses watched it, he would've seen lots and lots of guys making good money driving around collecting scrap metal, like what slayer over on hide5 does. It requires only any old pickup truck--but one with a big bed--and one's set to go, early in the mornings of garbage collection days, two or three hours before the professional sanitation men begin their rounds.
There's opportunities to collect some things for re-sale, but one has to be careful to not pick up so much of it that he spends more time selling and shipping such goods than picking up scrap metal. That can be a drag and a waste of time; better to just go for the quick pick-up-and-sale scrap metal