You listed two separate careers – web designing and web marketing.

If you are interested in pursuing a career in web marketing, I would strongly suggest getting a professional qualification at one of better web marketing programs in the country (somewhere like the University of Oregon – http://lcb.uoregon.edu/departments/mktg/index.html ) or possibly even an MBA in marketing. There is really not much money to be made in web marketing as a freelance or independent web marketer, unless you really establish yourself as an expert in the field by getting a top notch expert blog and building a high profile portfolio. However, if you get the right qualifications, you can posibly get a job at one of the big SEO or web marketing firms, which tend to be located either in the Boston/New York area, or in Silicon Valley. Salaries begin low ($30 to 40K), and the work is typically "grunt" work. However, you can build up to a six figure incombe, but that will take you time.

As regards being a web designer, the opportunities for freelance or independent work are much better, and you may not even need to go to school. The CIW qualifcation (http://www.ciwcertified.com/ ) is more than enough, and there are many online web design degrees or certificates which are available (check out http://www.worldwidelearn.com/ for some options). If you are going to set yourself up as an independent web designer, you are going to need to become well trained in several programming languages, get familiar with video and phot editing, and possibly even take a graphics art course or two from your local community college. As regards earning potential, that is going to be limited at the moment in the current economic climate, as businesses cut back on their marketing budgets (under which websites usually fall). However, you can make a reasonable income from web design on your own ($30 – 35K within the first year, if you are good), although you really have to concentrate on promoting yourself and establishing your credibility. Jobs with a web design firm are highly competitive, and are also under pressure from the economy. Firms normally hire on the basis of past experience with web design (so you might want to look at hunting for a job after you have had some experience out on your own and built up a portfolio), and usually want some sort of degree or qualification (although this differs from firm to firm). Salaries differ, but usually fall into the $45 to 55K range, with the top designers getting double or more than that.