These links are mostly from conversations in the Editorial Freelancers Association.
Happy surfing!
On the Basics: Tips for Getting Started in Editing or Freelancing
On the Basics: So You Want to be a Freelancer
On the Basics: So you Want to be an Editor (or Proofreader)
EditTools: Duplicate References – A Preview
When Is the Right Time to Launch a Freelance Tech Communications Business?