I'd like to be able to freelance full-time, essentially working for myself.
Get ready for a wild ride, wait 'till you see who your competition is - remember it's a **worldwide market** filled with a large buying sector eager to exploit, with many willing to let them. Don't get discouraged though, there are gems in the sand. You just have to dig hard and deep.
Working for yourself is nowhere near as glamorous as it looks from the outside. There are days I wish I was a workin' grunt again. :-) Two good reasons, if you want medical benefits you need to pay for them yourself, and you pay very dearly. Second good reason, all the bull-puckey that someone else usually deals with - accounting, dealing with customers, marketing and selling the company, (*ahem*) managing and motivating their employees - these, and more, are now **your** job.
I definitely need to trademark/copyright my business name- that's a given.
False, and expensive. Do this only if you feel the mark or name is something someone would steal. There's no sense in investing $450+ (more, if you use a lawyer) and a year of your life (which is about what it takes) if you aren't even sure this is the thing for you.
What you **do** have to do, generally, is register your business with your state. See your state's Secretary of State web site, register your business there. Some cities require local registration.
Open a separate bank account, keep your business stuff separate from domestic. Keep very close track of **all** of it - I suggest at the very least QuickBooks SimpleStart (and may be all you need.) You'll figure out why when April 14 rolls around.