If you are looking to make passive income on the internet then what you have to do is figure out a way to get natural, organic traffic to your website every day. If you can develop a system for getting people to visit your web properties, without having to pay for those visits, then you can probably make residual income from that traffic. Most any niche has at least some commercial intention behind it and therefore there will be advertisers who want to buy your traffic from you.
If you want to know how to make passive income then you need to create lasting content that will stand up over the test of time. If it is genuinely useful information then you can make money over and over again off of your articles and thus build up an income.