If you have an interest in some topic or a hobby, you can publish information related to that interest or hobby on a website. You then include contextual advertising on each page (like google adsense) and you get paid each time someone clicks on an ad. There is no maintenance to this since the ads are automatically generated and updated. You just keep adding pages to your site and sections to your site when you have the time to do so. If your site becomes popular enough, you can even add a blog or forum (although these require a bit more maintenance). If applicable, you can add on a shopping section with affiliate links (this requires periodic maintenance). Publishing this way can generate a few hundred dollars a month or over $1000 per month, depending on how popular your site becomes. It's a bit of work, but it's kind of fun since you are writing about things you have an interest in. It makes for a nice side income.