What you are talking about is Doing Business As (DBA):
Here are the Florida rules for DBA:
Choosing a DBA Start a Business
Register with the State: With a DBA/fictitious name you will be able to register the name with the state to conduct business with this name for the entire state. A lot of very small businesses choose this path, or those who are not sure if the company is going to fly and want to start small and work up to incorporating later.
What to Consider: If you choose the DBA as your filing, then name you choose can be used by another company. So the name is not to you alone in Florida. The other thing to consider is that if you file a DBA, there is no limited liability. What this may mean to you is that if someone sued the company, your personal assets would be available in a lawsuit. If this is not a concern then a DBA would be fine.
Legal Notice and Business License: Once you have the DBA filed with the state, then you will need to do a Legal Notice in a local newspaper, then obtain a business license with your county. A business license/occupational license or business tax receipt is required by most counties in Florida to have the legal ability to do have a business in that county. Check with your local tax collectors office to see what they require.
Unfortunately it looks like this is not as cheap as one would perhaps like, plan on spending $100-$150. Perhaps you might like to checkout a LLC as an alternative?