Started this project 1 year plus ago. I built a few websites and put in Google Adsense advertising (more info https://www.google.com/adsense/start).
It begins to pay off now. As of yesterday, I finally hit my 5 digits passive income online!
Not bad considering that this is 100% passive. I have not been touching these websites for the longest time.
If I can do it, you can do it too! The only way to fail is the failure to try. I did it 1 year ago and it pays off. I hope I have more time to do this. =)
SEO + Adsense = Passive Income!