A Question about Jobs...

[Lunadis]

Basically, you can change your job infinitely. The only drawback is when you change your job, it takes anywhere from 2 to 8 battles to adjust to your new job. Also, if your class didn't have MP before, it won't be there for your spells when you need it.

Stats change to whatever job you pick. If you change from Black Mage to Knight, you'll lose Intellect, Wisdom and whatnot and gain Str and Agi.

This only makes sense since it'd be no fun if players had to wait for a certain job to unlock late game.

"NOTE: Numbers by statistics are multipliers of the character's current EXP
Level. All characters at the same class and EXP level and equipment will
have the same values for all five perameters (Strength, Agility, Vitality,
Intellect and Wisdom) regardless of past experience."

EDIT - Oh, and your keep your job experience for that job when you change. That's why some may recommend you remain with a Monk for the whole game if you used it from the start VS switching to a Black Belt when such is unlocked. Same in terms of White Mage and Devout, Black Mage and Magus.