Ask HN: Your best passive income sources?

A supportive working wife, nothing beats that :)

Airbnb. High value customers and very little overhead on my part. Not totally passive, I guess, but takes up very little time and makes us a decent bit of money on the side.

Planscope (https://planscope.io) - predictable, more-growth-than-churn SaaS revenue

Compared to my book, which fizzles out when I'm not actively marketing it, building a B2B subscription product is the best, most turnkey income source I've ever had.

Facebook was definitely my biggest earner until they decided to crack down on everything at the end of last year and basically screwed everyone over.

It's the same deal for SEO, used to be a easy way to promote Adsense, CPA offers and what not, but the penguin change just makes it harder and harder to rank for keywords.

2012 has been definitely a slow year for Internet marketing, the worst I've faced since I started in 2006.

I have two sites that I built 3 years ago that still rank well for a few valuable keywords. Each site has hundreds of pages of content but one page on each site is number 1 on Google for keywords that pay $5-10 per click. Not a lot of traffic, but enough for a few hundred a month from adsense and affiliate links.