If you have previous experience as a computer programmer, or have skills in this field, then there is plenty of work you can pick up as a freelancer. If lack of confidence is holding you back, then Free Code Camp is an excellent way to get your foot in the coding door. This organization provides free courses where you will build real-life apps and programs, giving you experience and plenty to add to your CV.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.