I. Mule?s Errand
When your character reaches Level 15, go back to Flaris (the main town) and talk to Leily. She will ask you what job you wish to become, so choose Mercenary and she will give you a simple guide. Now you will have to speak with Valin, who is northwest from where you are now.

As you can see, Valin is a lazy man who has a huge appetite. Once you talk to Valin, he will ask you to visit Losha and bring him his lunch.

Losha is an NPC that sells Food and is located in the eastern circular hub of Flaris. Once you have the quest item in your inventory go back to Valin to move on to step two.

II. VisionStones, the Bravery Sword?s Ingredient
Valin now asks you to bring back the Bravery Sword from Boboko (Shield Seller).

Once you find Boboko he will ask you to collect 20 VisionStones from Grownup Lawolfs. As you are Level 15 now, it is easy for you to find them!

III. Forging the Bravery Sword
Once you have all 20 VisionStones in hand, return to Boboko and he shall give you the blade of the Bravery Sword. Now go back to Valin and present him with the Bravery Sword?s blade. He will then forge this blade into the Bravery Sword. Now you are now a Mercenary. Congratulations!