One of the most popular ways to earn income passively online is by starting a blog and monetizing it with affiliate links. You create a site about a topic you enjoy or have some knowledge about already. You add new content on a regular basis as you should with any blog. Then you sign up for affiliate programs for products or services related to your blog topic, and include affiliate links in your posts. You can also include links or banner ads in your WordPress blog sidebar for the affiliate programs.