While I applaud your initiative, I think you're still missing the point. Yes, there could be legal ramifications. But regardless of legal guidance or not, the decision is Admin's. This is his site. Everyone who runs a contest of some sort through here is recommended to ask for his blessing. If he isn't comfortable with it, it shouldn't be done (and likely won't last, because the posts will be removed).
I promise this isn't singling you out. This is told to everyone who posts a contest/giveaway/sweepstakes on the forums. Be patient, wait for his response, and go on from there, regardless of what outside sources say.
Edit to clarify my post. I understand, and hope everyone else does, that there could be serious legal ramifications when you ask entrants to pay a physical entrance fee (whether monetary, cards, whatever). I'm not a lawyer, I don't know all the rules and details, but I do know it's more complex than simply "send me this and be entered". Understand that even if all legal bases were covered and airtight, Admin may not be comfortable with this taking place on his site, and it would be polite to at least wait for his blessing before continuing.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.