It is work work not passive, but I write dev docs for $80/h. But it is simple work, you just go research and write. No Racoon calling out to Wingman to get user info provider services.
I write documentation for a living (a different, non-tech kind). The best resources in my opinion are the writing guides of various governments. Gov.uk leads the way, but the Australian government puts out great guides too.
Steve Krug's "Don't make me think" is old but still applies to the modern web.
