I took the opposite approach; I started on a whim
It wasn't long after I had started reading Steve's blog, I spent an afternoon thinking about what I would write about and why I wanted to keep a blog, and the next day I bought a domain name, hosting, and just went for it.
Admittedly, my initial goals were not to make money from blogging, but to keep track of my progress and to consciously build an online reputation. Making a few bucks along the way has definitely helped though!