I'm at the point now where the money that I make online constitutes the majority of my total income. However, I'm not yet at the "full time income" level. I consider $5K/month to be the minimum to constitute full time income, and I'm not quite there.
The most important thing that I've learned is that there has never been anything that I had put online that I haven't made at least something from, even if only a little bit.
The first thing that I ever did was to write an eBook and sell it on Amazon and Smashwords. I also made a Wordpress site, and sold it from there as well. I put very little effort into promoting the ebook, but somehow I managed to sell about 10 to 15 copies of that book in total.
I wrote about 7 other eBooks in total during my "not taking IM seriously, but still dabbling" years. I'd estimate that of all the eBooks that I wrote in those years, I sold maybe 50 to 75 copies in total. I put a ton of effort into writing them, but had no motivation to market them. I still made some sales nonetheless. The only "promotion" that I did was to have a link to my website in my forum signature for every forum that I posted on regularly.
There was no real strategy. I was motivated enough to write the books, but lost motivation when it came to promoting them, which is where 95% of the game is played.
I also dabbled in affiliate marketing. I made some videos about doing dirtbike mods, and I posted links to the parts that I used via amazon affiliate links. Again, I didn't really put that much energy into making a lot of money out of it, but I did make a bit of income. My best month of Amazon putting money into my bank was about $45, which happened a couple years ago. To this day, I still get a small bit a residual income each month from Amazon. This month they gave me $4.88 . It's not much, but it's something. Again, I was motivated enough to get started, but not enough to follow through and actually try to make a real business.
I read a cool ebook once where the writer of the book offered $15 in affiliate commission for each book sale you make. I made a post on a forum that I was a member of, and already posted on regularly. I did a book review, and I posted an affiliate link. I asked the forum admin for permission before doing so. I made about 4 affiliate sales on that over the course of 2 or 3 years.
I then decided to get serious. I picked a niche that I felt that I could stick with for many years, and I was determined to give it a real shot. I've spent the last 3 years sticking to just one thing and consistently putting effort into it. As a result, the income has been steadily growing each and every month every since I started, and has resulted in me now making a part-time living online .
The moral of the story is that it's pretty easy to make money online, even if only a little bit. If you can make a dollar or so, then you can make 2. If you can make 2, then you can probably make 10 or 20. If you can make 10 or 20, you could probably make 50, and so on...
I hear "5 years of taking it seriously" is a minimum requirement of becoming successful with this stuff. I'm on year 3, and that seems about right.
Just pick something and stick with it for 5 years minimum, and you will probably be successful.