I had a "hire me" link on my newsletter for a while (I recently took it down, because I am not available for the next few months). It seemed to be a moderately good strategy; I got multiple offers quickly after I got laid off.
[1] https://newsletter.taylor.town
Monetizing my newsletter doesn't sound appealing, but trends.vc seems to have a pretty successful thing going on.
I highly recommend reading this post from Ben Kuhn on the how and why of keeping a blog. Rather than focusing on a niche, it gives great advice on finding things to write about. Maybe start out developing a style first, and see what niche develops naturally?