Writing World's Getting Started: A Step-by-Step Guide to Launching Your Writing Career has informative articles on every single step of getting your freelance writing career off the ground. Topics include:
Begin at the Beginning
Queries and Submissions
Conducting Research and Interviews
Crafting Your Article
Rejection, Writer's Block, and Other Hazards of the Writing Life
Should You Quit Your Day Job?
Each topic has a long list of helpful articles, so check it out!