Merchant Training Quest
1. After you job change to Merchant, talk to the man named Guarnien close to the Merchant job change NPC.
2. If you accept his offer to train you, he'll require you to learn Enlarge Weight Limit Level 4 before he speaks with you again.
3. Return once you've gotten the skill, and Guarnien will talk to you about Item Appraisal, Mammonite, and Discount after giving you one Battle Axe.
4. Guarnien then asks you to learn Discount Level 4.
5. After learning the skill, come back to Guarnien, and he'll give you 830 Base EXP and 116 Job EXP.
6. Talk to him again, and he'll ask for the cheapest 10 Red Potions from a vendor in Prontera, and he'll proceed to warp you there.
Talk to them, and to get the best price you'll have to "cancel" in the dialogue box before getting the best price. (390 from Aigie or Sagle works; if Aigie offers potions at 340 Zeny, try the others. 340 Zeny is Novice Potions). Be careful not to mistake Novice Potions for Red Potions as they may give you those instead!
7. Bring him the 10 Red Potions, and he'll give you 1,120 Base EXP and 220 Job EXP.
8. Talk to Guarnien again, and he'll talk about Overcharge before asking you to learn Level 4.
9. After learning the skill, come back and talk to him, and he'll give you 1,260 Base EXP and 272 Job EXP.
10. Talk to him again, and he'll talk about Pushcart and ask you to learn Level 4.
11. Return after learning the skill, and he'll give you 1,620 Base EXP and 520 Job EXP.
12. Talk to him again, and he'll talk about Vending and ask you to learn level 4.
13. After learning the skill, talk to him again and he'll give 1,860 Base EXP and 604 Job EXP.