How often do cities refresh their job list

Here's a quote from another FF wiki:

In the iOS version, the quest is opened up after defeating Gutsco in the Molten Cave and reading all of the letters Topapa sends you up until that point.

Source

Base classes (no requirement)

• Chemist
• Squire

Chemist track

• Black Mage — Chemist 2
• Time Mage — Black Mage 3
• Summoner — Time Mage 3

• White Mage — Chemist 2
• Mystic — White Mage 3
• Orator — Mystic 3

• Arithmetician — Black Mage 5, Mystic 4, Time Mage 4, White Mage 5
• Bard — Orator 5, Summoner 5, Male charater

Squire track

• Archer — Squire 2
• Thief — Archer 3
• Dragoon — Thief 4

• Knight — Squire 2
• Monk — Knight 3
• Geomancer — Monk 4

• Ninja — Archer 4, Geomancer 2, Thief 5
• Samurai — Dragoon 2, Knight 4, Monk 5
• Dancer — Dragoon 5, Geomancer 5, Female character

Hybrid track

• Dark Knight — Black Mage ★, Dragoon 8, Geomancer 8, Knight ★, Ninja 8, 20 kills¹
• Mime — Chemist 8, Dragoon 5, Geomancer 5, Orator 5, Squire 8, Summoner 5
• Onion Knight — Chemist 6, Squire 6

^{Note 1: character must turn into a crystal to count as a kill.}