Ask to 90% of iRO Botters what class they use to farm and I can tell you, their answer will be Rogue.
The Auto Steal give a free item from the mob, no matter what is it, so when you kill 9000 monsters per day, you can guess that at least 5 will get it card stolen. Some people may also argue Mug is also a good skill to get money, but I never really could get anything more than 400z per Mob (Wasting SP and Time to do it), so if you really want money, make a Rogue and another account with a merchant selling loot to NPC and rare drops to players.
tadam.