The truth is that while there are those who are doing it, $100 a day isn't something that's "fly by night". Let's start with something more simple, more approachable.
I encourage everyone who is willing to post some tips or "How To"'s for people looking to earn money online. Let's start with something small like $5.
For those of you viewing this to learn how to make $100/day you should take the $5 advice others may be willing to share here, do it, and if successful replicate that success to meet your goals.
Posting small jobs that you know you could do on Fiverr.com
Visit this forum and other forums like it and offer to do some basic article writing.
Now sure, you may not want to work this way for the money. You may think that everyone sits back and lets a website bring in the cash but no matter the revenue source you still work. You post new content, you consider new objectives, you market and advertise, and all the sweet stuff in between.