Many bloggers think that they'll be the next Pat Flynn and be making $200,000 / month as he does. This is pretty unlikely. Contrary to popular opinion, blogging is not easy. Or rather, making lots of money for little effort is not easy. Much like a job, it depends on how good you are at it and how much effort you put in. If you want to give it a go it's probably best to start it alongside your current job and see how you get on for a few months.