You should consider your class when trying to make money..... so lets look over what already exists and how it should be played to get money.

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Knight
Vaga: If you wanna play a squishy f*** then yeah go for it, you burn more money on meds than anything else but hey at least your damage is good and your only AoE damage is half swing until 3rd Job change.... So yeah good luck with making money here.

Commander: Why???? Sure you take little to no damage but your kill speed is so slow. Don't worry though, you get an AoE at lvl 75 job change!

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Archer

Well if you decided to play one of these rare unicorns then more power to you because these have just as fast of a kill speed as a commander does. Well unless you wanna waste money on waters of course. No AoE till 3rd Job change and no poison cloud doesn't count!


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So this leaves us with two classes left!
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Theif
Hitman: This class is probably the worst money makers in the game when first starting out, dont bother. Its recommended for its 75+ AoE skill at 3rd job change.

IS: This is the best class as theif for fast money when first starting out (after 50+ of course). The reason to this is because of the skills it gets.

First is Dance of Killing also known as DoK which is a good 1v1 skill to use agaisnt mobs.
When you get Dance of Killing everyone will basicly want you to leech them at emok.
Price varies of course, but at the time of posting this I have been payed 1kk + cert (cert for more emok time) per hour on emok.

If you are good at your job and ur stats are placed (specificly for solo kill) correctly, then you should have no problem doing 1v1 on emok ghosts without the need of healer (you will spend money on meds tho... alot) . ( also if you have the gear, I recommended getting lvl 55 and getting full g55 free gear from quests 50-54 )

To increase your kill rate as a thief i recommend only using DoK because it consumes about 120 mana compared to your other skills which will drain your mana rapidly. Thus the results ends with less sitting, less mana used, better kill rate to mana ratio, happy leecher. its a win win... win..... win.

After hitting lvl 68 you have maxed out your CO. This will allow you to lure mobs and have a high damaging AoE. This doesnt kill all the mobs though, but it will reduce their hp to 0 without killing them and then they can be finished off with a spin attack.

At this point you should know what you need to do for cash as theif

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Mage

Oh the mage, the wonderful mage. Easiest way to get money.... once you hit lvl 34 of course

Splashy splashy splashy and then splashy some more. Doesnt matter if you are cjb or hermit.

If you decide to splash as a C-J-B, good luck cause its your only AoE skill

a hermit on the other hand...

you get IR at 56, chain lighting at 59 and then storms at 65

So because of daily quests you can probably splash from levels 46 to 56 in the doggebi woods (area in front of d1). This area should always have someone willing to lure for you.

At 56 when you have IR, you can pretty mage do any area you want up to red mobs ( so not to die or waste meds) I on the other hand would probably recommend dungeon 3 floor 1 - just lure everything and then kill your lure near the floor 2 stairs so in case of emergencys you can run into the safe area. This is do-able proably until 66 when things start to turn grey.

At lvl 59 you can use chain lighting to kill woods, not the best of money but it can help you get started on your elements quest and imperfects sell for about 120,000 geons each. On average by the time that i gathered 20 imperfect elements i had racked in about 300,000 - 400,000 geons

A good alternative to Forest of Elements would be floor 3 crows. Granite you have enough evasion I would do crows until they are grey.

Good luck, and have fun.