Helen - there's been a lot of good advice here that I won't attempt to repeat. I would like to add something a little different you might want to consider.
I've always made a distinction between freelancing and running a business. I know that technically and legally there's really no difference, but here's what I mean:
If you are a freelancer, then you will be contracting yourself out to perform a certain task. You might work for other design firms or for a company with an in-house web team that you'd interface with. You don't have any plans beyond being a one-woman show and supporting yourself by trading your time for money.
I look at running a business as being consultant paid to produce a certain result. It involves being able to understand and solve a client's bottom line business issues, using your expertise in web technology and internet marketing. The typical client would be businesses, corporations and non-profits who have no in-house web resources available to them. The ultimate goal would be to eventually hire freelancers (like above) to replace yourself, in order to work on your business rather than in it.
I think this is important to know, not only to determine who your target client will be, but also to establish future goals, write a business plan, etc.
No matter which path you take, you'll have to figure out how to find and be found by your clients (marketing) and how to reach an agreement to do business with those client (selling). Personally, I feel that learning how to market and sell is more crucial if you are pursing the "business" concept rather than freelancing.
Here's a couple of resources that might be helpful:
The Web Design Business Kit
A great resource for either freelancing or becoming a business person.
I highly recommend this if you're looking to pursue the business model and need to learn how to sell your services to decision makers.
Hope that helps.
[edited by: stuntdubl at 9:50 pm (utc) on June 16, 2004]
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