Hmmms... I will tell you all that I know...
Hunter gets hired by trader to protect them... so the trader can just stay infront to lead the camel or stay on top of the camel without needing to kill the NPC thief that spawns and attack the camel or you... Hunters get hunter xp by killing thieves (be it NPC or Player). But you can just offer help to fight off the NPC thief for free

Mostly trader will hire a hunter when they are doing 2 star trade or above or just is a beginner trader. It is quite hard for you to be a level 20 hunter as player thief may kill you easily.
Thief in the other hand 2 stars and above trader. When the trader dies or when the camel dies, the goods will be dropped on the floor. The thief have to summon a camel and pick up all the goods, then go to the bandit den to sell the goods to earn thief xp and money. Thief xp can also be gained by killing hunters.
I hope this information is enough for you to know about these 2 jobs.
My english is bad.. Pardon me
