Same boat here, I only have to work about 2 hours per week to maintain $500K annual profit. I'm the biggest procrastinator in the world and don't know how to program (although I'm now learning just for fun).
Basically content marketing. Researched an industry very, very deeply and summarized the important concepts, tactics, and strategies one should follow to save money or save time within that category.
Make the content free - attracting a large audience, and recommend the best online services that help with that particular vertical (affiliate marketing/lead generation).
The 2 hours per week is just summarizing anything new that happened that week.
This is not a get-rich-quick thing, took almost 10 years to get to this point, and huge amount of focus on this one thing - and I've truly become one of the leading experts in this vertical.
I am more interested in the process of finding and selecting a niche in general, how did you do that? How did you stay committed all those years unsure about whether working in your niche would even be viable?
Most important thing is to go into a category that already has lots of competition. It's counter-intuitive, but this is important. The thing you want to do is slice out a niche within that category that you fully own. It could be information on getting the best price, or info related to your own city/region. Once you get a small foothold in that niche within the category, you can expand and grow within that category.
Is traffic to your site mostly from Google searches, and if so, could you say what you found to be the most effective method of improving your ranking in the search results?