I blog, but more as a tool for my business, and I blog about my speciality.
I don't really do affiliate or sponsored blog content, but it definitely wins us clients for big projects, and off the back of the blog I've received paid writing and speaking jobs which in turn create more PR for my business.
Like others have said, you can't earn anything unless you just start blogging! Make sure to make every post filled with your personality, and definitely invest in your imagery/photography (maybe take a class online if you have time!).
I also work with brands who pay bloggers for content - the better the imagery, the more likely you are to be picked for paid collabs.