Can minors sign binding work contracts?
Even if yes, those contracts would have to be lucrative.
Otherwise, what minor would ever sign?
Adams signed, Mines signed. Freddy Adu signed. Plenty of kids turn pro before they turn 18.
I'm no contract lawyer, but maybe since they are under 18 their parent/guardian has to sign.
As far as how lucrative it has to be, I guess that depends on the kid and what options he has. In Mines' case, he apparently had a full ride to Stanford; the offer from RBNY had to be pretty good to get him to pass on that. Other kids may not have such good options and would take much less.