Thank you all for your replies.
Update: I didn't end up accepting the offer of $750, saying that the topic is important to me and I don't feel comfortable selling without knowing what they're going to do with it. (Maybe if it were a super-high offer I would be more inclined, lol!) I thought I would eventually try to do something with it myself.
This month I received an initial offer via DomainAgents.com for $800. I haven't responded yet and they've increased to $1000. I assume this is a different buyer, but who knows, maybe the commission is lower with these agents. I don't know yet if I'll decline or counteroffer a huge amount.
Honestly if I found someone who wanted to collaborate on something and I really believed in their approach, I might not ask for a lot of cash. But that's probably a lovely thought that would be hard to make a lovely reality.
So I've just read MMM's post from 2013 (like 6 years old):
https://www.mrmoneymustache.com/2013/01/17/how-to-start-a-blog/. One thing I'm not clear on yet is whether or not to use WordPress (probably with Bluehost), because I don't understand if they limit flexibility in terms of monetizing.
I have started planning some topics for content. The actual writing will be a key piece of this... let's see how that goes!