You mean Gerard Pique? Rumors have it that he did however both are in committed relationships so it is highly unlikely.

You need to be at least 19 in order to join the NBA. Many players go to college for a year before joining the NBA. That is the only requirement. In Europe, you can join a pro league as long as you have the skill, age doesn't matter. Think Ricky Rubio.

There are no educational requirements to be a pro soccer player. However, if you are underage and join a pro club, you must finish your basic schooling while still being a member of the team. Underage players have mandatory school days. In the US, most players go to college before joining the MLS.