The real answer to that question has more to do with the type of freelance business you want to build. For the purposes of this post, we'll assume that you are focusing on handling the weekly or month-to-month bookkeeping of your clients as their primary bookkeeper.
You've Got Options
From my experience, I've found that most freelance bookkeepers main concern is with the technical skills needed to provide quality service. And yes, that is a good place to start.
If you're starting from zero, the bookkeeper's credentials start academically. Here are a few choices to consider: