If you have a background in a specific field, you may find there is a demand for writing industry papers in your area of expertise. For example, there are often adverts for doctors, lawyers, nutritionists, and business experts from particular niches, to write white papers on different subject areas. These are well paid jobs that you will need to stake your reputation on, but that can often be worked on from the comfort of your own home.
No matter what method you select for generating your online income, there's one very important thing to understand. Today, across this globe, with its 7+ billion inhabitants, there are two recurring things that people are looking for more of. Either people want more time or they want more money. The truth? Time is far more valuable than money. You can't recreate time. Once it's spent, it's gone forever. Not money.
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.