Look at all the people that went to school, accumulated thousands of dollars in debt, and now do something not even remotely related to their degree. What's even worse is these people are typically working dead end jobs. Jobs that will never make them enough money to settle the debt from their school loans. How did they wind up here? They didn't have a clear and definite purpose when they started school. Things got hard and they probably changed their major. Some dropped out. Some finished but didn't take the next logical step.
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.