There is a lot of money to be made by blogging. How much depends largely on how much effort you are willing to put into them. But your efforts will continue to pay for years to come.
I currently have close to 20 web sites. Many of those are blogs. The blogs are my highest earning sites. I actually have many different blogs, each one being on a separate topic. Some earn a dollar a day, others earn $10 or more a day. And it varys. By having multiple blogs, I usually have something to write about. The cool thing about blogs, is that I can write a post, and it might continue to get traffic for many years. This is called residual income. The more posts I have, the more traffic I might get, and the more money I might earn. I could stop working one them, and continue to earn money for a long time.