TypeA vs. TypeB - Money Topics vs. Hobby Topics
Since writing Building a Business Around Affiliate Programs, I have been criticized many times for suggesting people work on hobby topics first. Though I can certainly take the criticism, I believe the critics didn't realize I had written that post in response to many questions during that time from beginners. I still stand by the recommendation today, especially for someone working on their first site, though I realize this path is not for everyone.
Type A Sites - Just For The Money
These types of sites are for high dollar clicks and returns. Topics like finance and loans, hosting and domains, gambling, etc. If you are a seasoned internet veteran, and don't mind swimming with the sharks, go for it. What I mean by swimming with the sharks is this: When working in these competitive areas, you may end up dealing with unscrupulous webmasters. Some of these types will spamreport you for the appearance of the most minor infractions, run clickbots on your ppc campaigns, 302 hijack your ranks, steal your content and whatever else they can do to get ahead of you. It just goes with the territory.
However, the money is there, and it's all open and fair game. If your sole motivation is the bottom line, or if you just get a rush from the drive of this level of the game, maybe it's for you. I remember reading someone's comment about this that was something to the effect of, "I can be highly interested in any topic, provided it makes great money." I'm sure that's an honest perspective, and there certainly isn't anything wrong with it. I play a bit in a couple of these types of areas as well, but they aren't my favorite.
Type B Sites - Something You Have Interest In
Building a site about something you're very knowledgeable and interested in, or something you wish to learn about can toss a thrill into the mix. I learned a long time ago, if I can get up and look forward to going in and getting to work (as long as I am making a living at it), I win. If I'm learning about something new, I am much more likely to have fun writing about it or working on a site about it. If my business involves a hobby or other interest, I will have a different attitude towards my business, and it will show. I love cars, engines, and horsepower. I could probably write about them all day without flinching. In contrast, I find no joy in writing yet another finance options article.
The trick is, to find something you're interested in, that makes decent money as well. Find a good mix between both types A and B, and you'll most likely have a winner. For instance, back in the day I used to be heavily into the dating category. I was single then, and had a blast during my dating days, so I had fun building sites and writing about dating. It was a very lucrative topic to be in, and those sites performed very well for me.
When you get right down to it, it doesn't really matter if you build a site just for the money, or for fun while making money. As long as you do what is right for you, you'll be fine. As some shoe company says, Just Do It.