I am going to start giving a weekly tip to everyone who wants to do or learn to do this.
TIP #1: Do you live in a city? Drive around on trash day and see what you find. This is where I get most of my stuff. My friend just found a bike that sells for $200 in the trash of a rich neighborhood and it was just missing a seat. Hell, even if its beyond repair pick it up and take it to the scrap yard. They'll give you a few bucks for it.