Go to Sunbiz.org to get your LLC, Its like $260 in FL, I can't rememeber the actual amount, but I know its not more than $300. Then go to the IRS.gov to get your EIN, open an account with chase(you get a free safety deposit box, free printed checks for bus or personal account. There's other benefits that I can't remember right now).
Then go to Ups store and get you a mailbox (You might want to do this first, Sunbiz charges you like $10-$20 if you need to change your address after the fact, the only time its free is when you file your annual report. They charge you for that, so its nothing extra to update your address), A UPS mailbox is the only "po box" that you can use for your business address, you're not allowed to use the ones from the USPS. Its about $260 or so, and they give you 3 months free, so you're good for 15 months. Your address wont be xxx xxx p.o box 555, it'll be xxx xxx # 888. So it looks official like a office or unit number.
Save all your receipts or make copies and expense as much as you can come tax time. You can use Turbo tax online to do you business and personal taxes together. You just follow the steps and input all your info. Its $100.00