Here are some Job Requirements for Final Fantasy Tactics
Chemist=Free
Knight=Squire Lv.2
Archer=Warrior Lv.2
Wizard=Chemist Lv.2
Priest= Chemist Lv.2
Monk=Knight Lv3
Time Mage=Wizard Lv.3
Oracle=Priest Lv.3
Summoner=Time Mage Lv.3
Mediator=Oraclelvl.3
Geomancer=Monk Lv.4
Thief=Archer Lv.3
Lancer=Thief Lv.4
Ninja=Archer Lv.4, thief Lv.5, Geomancer Lv.2
Singer (female only)=Mediator Lv.5, Summoner Lv.5
Bard (male only)=Mediator Lv.5, Summoner Lv.5
Samurai=Knight lvl. 4, monk lvl. 5, Lancer lvl. 2
Mathmatician=Priest lvl.5, Wizard lvl. 5, time mage lvl. 4, Oracle lvl 4.
Mimic=Knight Lv.8, Chemist Lv.8, Summoner Lv.5, Mediator Lv.5, Geomancer Lv.5, Lancer Lv5
That's pretty much all the abilities