I also want to say the phrase "passive" is somewhat misleading. You have to push pretty hard to get that ball rolling. You can start a podcast for the price of an Xbox and a couple of games. With a podcast people can hear you. it makes you more real. I had a blog for years and a email list over 1000. When I turned that same information into a podcast, and people could hear my sarcasm instead of reading italic words, they began to know, like, and trust me at a much quicker rate. With the right niche and affiliate product you can make some nice cash. The beauty of podcasting is you post the audio/video once and its there until you take it down. Try and make evergreen content.