I'm glad to see you've come around. I'd just like to give my two cents here as I was a lot like you and started doing design work when I was 15 and 9 years later I'm the VP of User Experience at a successful web application development company.
The first bit of advice I can give is that you must first learn to know what you don't know. That is, understand that your knowledge base is limited and seek advice from others as much as possible. Things like getting good statements of work for all jobs you do and making the client pay forward are things better to understand before rather than learning from the school of hard knocks.
Second, you are young now but rapidly your life is going to change. You WILL be in a completely different place in your life in 5 years than you believe. Nothing goes according to plan so the best you can do is make good choices along the way and try your best to achieve every goal. Don't make lofty goals with no plan on how to reach them. Make goals then set milestones to reach along the way.
On the specific issue of doing design work there are a few things to consider. Great designers don't need $11,000 worth of hardware to do their job. They don't need the latest and greatest computers. To prove this just go down to the local art museum or look at the great artwork made (on computers) over the last 10 years. Look at Toy Story the movie which was made on computers likely less powerful than an iPhone! When I started, my first real computer was a 5x86 133mhz running windows 95 and photoshop 3. I had 12mb of ram and a 1mb video card! I upgraded throughout the years but it wasn't until this year that I bought my first brand new top of the line machine. The truth is, I understood the technology better and appreciated what I had more when I had to struggle for it all.
And that's the most important thing you can do. Struggle. Work your ass off. Work 16 hours a day for a few weeks to make something perfect. Strive for the impossible and never give in. Don't do this because it seems like a good source for quick cash... do this because it's what you love and the rest will come naturally.
And to the person saying that a $1,000 web site is a big job requiring many many people, don't listen to them. You need to gauge where your level is and charge accordingly. My advice is to not get too bogged down into support contracts where you make x number of dollars per month to do n number of updates. It's a time suck. Don't get sucked in! You will lose more money and time doing this. If you are a beginner a $1,000 web site might seem like a great deal but as you advance you need to understand that a real company wouldn't touch a $1,000 web site. There are many reasons which if you wanted to understand better you can send me a PM and we can talk. The biggest protection you can have is to meet with clients and explain everything you're going to do, write it up into a statement of work, attach a price and a deadline, list out what they need to provide you before work begins (partial payment and any content you'll need) and then get them to sign it. This protects your ass big time and alleviates questions as to what you were supposed to do for them where they expected more than you provided etc.
Ok, rant over. Good luck!
And for what it's worth, get a MBP and a 24" dell LCD. You'll be set. You don't NEED a 30". Trust me.
(Why not spend some of that money on fun eh? Thats a lot of dinners at Ruby Tuesday) But seriously reconsider what you really need.
