Being a freelance writer is easy, which makes earning from it also easy. On the other hand, there is what we call, "blogging." Freelance writing and blogging are pretty much the same. Blogging and being a freelance writer involves writing a lot and allows you to do it on your own chosen time. You can monetize (make money out of it) both of these activities, the difference is in the way you can make money out of them.
Blogging can be a hobby or can be a source of income, but it takes time. If you blog, writing skills can be a great asset but it is not the only necessary arsenal you need to posses. To earn money through blogging, you've got to familiarize yourself with SEO(Search Engine Optimization), SEM(Search Engine Marketing), ads and affiliate programs. The main advantage of blogging is that you can monetize your content for a very long time.
Being a freelance writer is really easy, there are a lot of websites that offer freelance writing jobs. All you need to do is register and then you can either wait for projects to be given to you or you can bid on a writing project. It really depends on the system of the website you've registered for. The main advantage of freelance writing comes from the fact that all you really need is to know how to write "good articles." Knowledge of SEO is a plus but not a necessity. Another advantage is that you will be paid immediately after you have completed a project. The downside is that once you're paid for what you wrote, you will lose all rights to it.
Blogging and freelance writing can help you earn and if you're really dedicated, it can help you earn enough to quit your job. The only thing you've got to remember is that you should first decide which of these activities are worth your time and effort.