Good points all!
I just read a REALLY good thread about something related.
If you can't think of a niche you KNOW about and are passionate about,
what about something you are passionate about LEARNING more about.
For instance you've always been curious about geneology or rock climbing or
speaking Spanish and want to learn how to do it. You could research it,
learn about it, write about what you discover and monetize the info with affiliate links.
If you find it interesting and something you've always wanted to
learn about anyway you can find some joy in researching and
earn as you learn - or learn as you earn!
The other idea in the article is to leverage off a topic that one of your friends or family knows lots about or is passionate about. Use their enthusiasm for the topic, hobby or whatever to gather ideas for things to write about, interview them and/or get them to write articles for you.