Good point, maximillianos. People find they really don't want to sell a product, but a service or the other way around. Or, they don't want to work with consumers, but retailers. Or the other way around. Or, they really don't have a good idea of what they want to do.
I work as a business consultant to professionals (Lawyers, doctors, engineers, accountants). I've done it for 11 years now. Typically, people call me on recommendations from others. That <cough> has it issues in getting new biz. Three years ago, I fell into "doing web sites." I have two people I can call in for the geekier stuff (db work is beyond me) and use templates or call in a graphic designer, otherwise I'm doing what I was before. It's ok to get "off track" if the track is not running where you need to go.
Building a web site is an excellent way to work your way though many of the issues that a good business plan requires, and it's a lot more fun than doing a business plan.
If you want a good guide to building a web site, look for a good guide to building a basic business plan.