I finance my parts buying with parts buying. I'll start out with X money, and buy some parts at the junkyard. Through the magic of ebay, on say $50 to started out spending, I may turn around $150 (I NEVER buy anything to sell unless I know up front I'm going to AT LEAST double my money). I take the initial $50 I spent, put it back in my wallet and go shopping for parts again. That $100 profit goes into my PayPal account, and when I've accumulated $200-300, I go shopping for a big ticket item. People that don't know squat about these rigs can be really hosed by those of us that know them, and know what parts can bring. I also don't sell anything that I think will be a pain in the a$$ to ship. Small, high demand items, such as rear seat hold-downs for example, are the ultimate score.
I'm blue collar like the rest of us, and a little cash doesn't go far. I prefer to make my spending money from the guy that doesn't know what he's selling me for $5.