I sold a Shining Charizard for about $200. I had no idea it was worth that much and I just had it rotting in a box, not even in a sleeve, in the basement. When I realized what it was worth, I swooped in to immediately rescue it. XD

I had a few other Pokemon TCG cards, but they were not in the best shape. I didn't put them in sleeves, so the holographic foil in most cases got really scratched and beat up. Plus they were heavily played with, so that's definitely going to butcher their worth.

Also, rummage sales are a GREAT source of cards. Most people there will skip by them, but there's hidden gold in these things in you know how and where to sell them. Lots of unaware parents getting rid of their kid's stuff and lots of unaware church volunteers could be your golden opportunity.