Let me get this straight: you want somebody to code a game (based on copyrighted and trademarked characters) from the ground up for you for free, and then as a "reward" for all of that effort, you offer a chance to act as the support staff for the game, also for free?
Pardon my saying so, but it seems to me that the incentive here is pretty darned small. Anyone capable of pulling it off would be a lot better off doing it without you. Ideas are worthless by themselves; it's execution that gives them value, and you are placing a value of zero on execution. Less than zero, really, if you are expecting the developer to become an administrator as well. You're talking about weeks (or months) of work. I'd expect that even a kid in high school would have more sense than to walk into a deal on terms like these.