If you want to learn how to do it in more details, I would recommend reading this SEO Guide.
For diversity, you can add a couple of links from Web Directories like botw.org, spoke.com, aboutus.com, blogarama.com. Even if Google doesn’t want to rank them well anymore.
Post some links on your niche forums also.
If you want to learn more about How to Create Passive Income.
If you don’t have enough time, you can outsource your SEO to an external service, just be sure that those guys know what they doing and require reports regularly.
Your online passive income business will grow slowly but steady. Once your websites will get high ranks, you’ll get more and more income every day.
One crucial thing here: you MUST build backlinks, lack of them will lead to wasting of your time and money.
Keyword research should not be forgotten also.
Follow this strategy and you will get your ranks and money.
There are more ways to construct your passive income money machine. One of them is YouTube.