I'm 14, and like most teenagers, I'm a freelancer. However, like grandmaster pointed out, get a portfolio! I have done many of my sites for free. However, they are .com's and .net's.
When you first are getting started, if you tell the person, "hey, I'm doing this for my portfolio", then you will paid well what you're worth. What a webmaster is worth depends on what he can do, what he is willing to do, how fast, and how well he can do it. You could put two people on a bid, and one can do said job in two weeks, and one in four. The one who can offer in two will get the job. But, don't set your deadline too short, you always gotta leave room for murphy! If anyone has not run into Murphy, you're not a developer...
Your portfolio will tell what you're worth. Every developer is different, and worth different. I know PHP/MySQL and can develop big, user driven, complex online applications. I might get paid 3000 for a CMS/user oriented site, but when I have someone come to me and ask for a simple five page site for their myhomebusiness.com, I'm not going to say, "Well, I'm worth 50 dollars an hour.", I'm going to say, "Ok, how about 500, and I'll host it and optionally maintain it for 30/month."
Keep in mind, at the age we're at, we can't afford to be too high. If we did it for free, and we have a dynamite portfolio in 4-5 years, we will get paid for all of our work many times over!