Assuming you don't already know how to build websites, I'd suggest you go to
www.macromedia.com and buy the latest version of Dreamweaver.
Next, enroll in Macromedia's online university. For $400 or so a year, you'll have access to classes for everything from basic HTML to ASP, Coldfusion, SQL, and more. Classes are either self-taught, or there are also instructor-led classes. I was really impressed with the courses I took.
My site (
www.gunshopfinder.com) is bringing in as much money as the time I have allows. If I could be on the phones eight hours a day, it would be bringing in much more. Today was a very good day.
The problem with my site, and something you may want to consider, is that it's very time-intensive. Making phone calls to get people to pay to renew means lots of "call me back next week" responses.
If I were doing it all over again, or if I were to start a new site (which I might do), I would come up with an idea for a site that would attract a lot of visitors (mine has over 200,000 a month) but also be appealing to advertisers. There are site owners out there who are making $10,000 or more a month from advertising.
Find the right advertisers is hard, so you may want to base your site's niche on a topic that advertisers will pay good money for. At the same time, though, your site has to be unique enough to attract visitors. It's a difficult thing to balance.
Some niches that do well are travel, computer-related stuff, and porn.
I'd also advise you to construct your site with search engines in mind. Before you build it, spend some time on webmasterworld.com. You can learn a lot. Almost all of my traffic comes from search engines. Roughly half comes from Google. That's free advertising if you do it right.
Give yourself a reasonable period of time before you expect to be making good money. I was delusional when I thought I could have my site start generating a liveable income within a year. It's been up for two years now, and I still have to do other work to pay the bills. I expect it's going to be at least another year, probably two, before I could quit my other jobs.
Hosting can be as little as $5 a month. I pay $500 a year, but that's because my site uses a SQL Server database.
If you're only in it for the money, another option is to have several small sites that rank well in the search engines, and have a lot of advertising on them. There are some webmasters who design what are basically useless sites, so that visitors look at them quickly, then click on the ads.