Matt,
Don't panic!
Like you I love the idea of running a profitable website. I have made two attempts and both failed, but don't worry something like 80% of all businesses fail!
Looking back I can see where I went wrong. I was in it for the money, I just wanted money and not add any social value (this is important to do well I think) so I stepped back and said to myself "what is a simple, common problem, with a simple solution that could be useful that I could create"
Within a few days I had the answer.
I have very little html knowledge, so I got a free script and paid a coder $500 to rebuild it to my liking. Did it work? I'll let you know! I haven't launched yet, because I got so busy at work, but it's definatley my primary goal.
Whatever you do, do it because you enjoy it or think you will, don't do it for money (although have a way to make money from it) but do it to help others. The big home runs online are usually hit by people solving their own problems where millions of others have the same problem.
Check this out
evhead: Ten Rules for Web Startups
Enjoy!
Max Power
"I can show you the path, only you can work it"