Serious raiding takes three things: Money, Time and Commitment. In WoW, monitoring these three factors is usually more important than your mana bar. Time and Commitment are the easiest to understand, you need to be able/willing to schedule 3-5 hour blocks multiple times a week, and commitment entails the desire to stick it out through wipes, bad luck, and fellow members disappointing you.
Money however is often at first overlooked as being a significant raiding factor. Casual players spend the majority of their time on low risk/high reward activities (like soloing or short instances), where it's a lot easier to earn money and where you don't usually have to spend much. A hardcore doesn't worry about it as much either since they have such a crazy amount of time they're willing to invest in WoW; while they may suffer high costs from raiding they have the most revenue streams available to them (especially once they put content on "farm"). However, money management is dangerous for the "semi-serious" raider; since we are spending most of our available time in groups (high costs), while not having as much solo-time to replenish our reserves (low profits).
So how should a semi-serious player make money? In WoW, you can earn gold either actively (ex: daily quests) or passively (ex: buying and reselling something on the AH), or some sort of mixture (farming mats then selling the item). In Burning Crusade I was quite adept at making money, but most of it involved working in Outlands, like completing quests at the level cap, grinding faction rep, or daily quest circuits. Very "active" sources of money-making. But I also raided a lot more casually back then, so I had extra time which I won't have in Wrath. Furthermore, one of my goals is to eliminate worrying about costs when it comes to raiding; if my guild requires ___, I want to supply it without any hand-wringing. If I'm going to raid seriously, and I'll be spending most of my free time in raids, I'll need to step up my passive money generation.
It's my theory that the best way to "passively" make money in WoW is to have access to multiple professions, which requires access to multiple high-level characters. My next post will explain how I'm going to manage this.