There is no retarded ideas in my opinion. Taking action is a huge step. If you search for anything online, and I mean anything, you will get results. Almost every one of the sites in the first spot is making money some how. There are tons of ways to make money with a website, and I am not even going to go into that, but almost every site online is making money some how.
All I am getting at is, you have to start somewhere, and if you are interested in that niche, go for it.
Do you have micro niche finder? I like to use it for the brainstorming mode. It will give you some off the wall ideas. I don't follow the rules about which ones to go after, I like to go after the 10,000 plus monthly searches because they are a little more of a challenge, but they yield a better return in my opinion.
If you don't have micro niche finder, just go to Google and type in the letter A, B, C, ETC. It will give you results for highly searched terms. When you find something that interests you, do a little keyword research and go from there.
The hardest part is the first step. One last thing I will say is, if this is your first blog, make it about something that you are semi interested in. Something that you can build on for a long time.
Good Luck.