Google AdSense might be the fastest and easiest way for a beginner to start earning passive income with a blog. The basic idea behind AdSense is that you can display Google Ads on your website and when a visitor clicks on those ads you get a percentage of the ad costs. You've certainly seen ads on other people's websites; you can have these ads appear on your blog or website as well.
Working with advertising networks isn’t your only option when it comes to selling ads. If you end up with enough traffic, advertisers may come directly to you and ask you to place their ad on your site. You can also contact advertisers yourself. The biggest difference from the above mentioned option is that there is no middle man, which means you can set your own ad rates.