First of all, your brother would have to consent to the sale of his interest in the condo. Find a real estate attorney licensed in Florida.
Prior to starting a business entity, you're also going to want to discuss issues like tax implications with an accountant. An LLC is probably the way to go, but you should be fully informed before you form such an entity. Assuming your brother is agreeable to the transaction, you may want to transfer ownership of the condo to whatever business entity you form. That way, you're shielded from personal liability in the event anything happens.
DISCLAIMER: Brandy A. Peeples is licensed to practice law in the State of Maryland. This answer is being provided for informational purposes only and the laws of your jurisdiction may differ. This answer based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. Under no circumstances does this answer constitute the establishment of an attorney-client relationship. For legal advice relating to your specific situation, I strongly urge you to consult with an attorney in your area. NO COMMUNICATIONS WITH ME ARE TO BE CONSTRUED AS ARISING FROM AN ATTORNEY-CLIENT RELATIONSHIP AND NO ATTORNEY-CLIENT RELATIONSHIP WILL BE ESTABLISHED WITH ME UNLESS I HAVE EXPRESSLY AGREED TO UNDERTAKE YOUR REPRESENTATION, WHICH INCLUDES THE EXECUTION OF A WRITTEN AGREEMENT OF RETAINER.