Article on Lifehacker about someone earning a living by buying and selling used appliances: http://lifehacker.com/how-i-earn-my-living-buying-and-selling-appliances-on-c-555205905.
My uncle did this years ago, in Hong Kong, before such things as the internet and Craigslist exist. My understanding is that he would go door to door and ask if the families would like to sell their used appliances. After a while, I think the family also knows him and would call him if they are interested in selling the appliances. As the article from Lifehacker describes, my uncle also would either fix the appliance and resell, or tear it down and sell the metal.
I remember he would gave us a lot of magnets to play with when I was a kid. Magnets that you would get from tearing out the strip that seals the refrigerator door.