It's a tricky business. Speaking as a web developer, you might think I'm just saying this because I want to improve my revenues, but I'm not - if you want a webstore to be successful on the web, you gotta pay someone who knows what they're doing to do it for you. Same goes for any complex website. I haven't seen a clothing Web site that can compete with a well-designed paper catalog for speed and convenience. And if you selectively block cookies like I do, you can't make your way around web catalogs.
Most rock bands make good money on affiliate marketing.
If you're going to spend time affiliating with other sites, I think you should also spend time putting together a site newsletter too. I think ezines work v.well. Check out Hard to Find Records and see what I mean. It's continued making a profit after going online. Hobbies can be profitable as well as give you a great reputation.