You've been offered some great resources here - I would only like to add that blogging is probably not going to be the cornerstone of your monthly income - no matter how great you are at it. You can make 'extra' money once in a while, sure. But a blog, at least from a business owner/VA standpoint should really be a tool for bringing more visitors to your website and showcasing your knowledge, understanding of technology or recent internet developments (whatever relates to your interests/niche/specialties, etc.) and/or provide tips and tools for whoever your intended audience is (most likely clients and potential clients).
There are some great posts right here in this section about blogging and what other VAs focus on when they post to their own blogs - so do check it out.
And, if you want a great place to start a free blog (and have an instant audience) you can create your own blog right here on the forums - click
here and then click 'Your Blog' in the menu along the *left side* of the page to get started.