I've been a dealer of Disney memorabilia since 1986. I've sold through a mail-order catalog (pre-Internet days), online through my website and Ebay and at various collectible shows from New York to Virginia. Many of the items I sold for a profit were purchased new at WDW. We used to go down with one empty suitcase and pack it full for the trip home. Several times, we shipped our purchases home.
All of that said, the market has gotten much tougher in the past couple of years. Most of the collectibles shows have died out due to Ebay and the Internet.
If you still want to do this, I'd suggest focusing on certain types of items. Limited edition items with small edition sizes. For example, ignore something that is a ltd. ed. of 100,000. That isn't limited. But a pin that is limited to 2,500 has a reasonable chance of turning a profit.
Items made for special events are also good - Grad Nite, etc.
Steve