Sythan

This is correct yes. Humans can take any profession up to Adept if they choose no profession. If you have one profession, though, the xp cap for all the other professions is lowered.

There is also the bonus profession. If you've played for 250 hours on a persona, you can have a third profession with no cost to the others. It's a bonus. (Currently I only use the bonus and not the primary or secondary professions slots).