First thing you need to do is register with the County tax office you are located in along with the State tax office. If you are in Lake County and if you rent a house under 6 months, you need to charge the tenant 7% Florida State Tax sale's tax and 4% Lake County Sale's tax. If you rent over 6 months, you do not owe any sale's tax. In addition, you need to have a business license from the County and the State. If you are located in Lake County, you can go to Laketax.com for information. The Florida State website is
Welcome to the Florida Department of Revenue web site which has plenty of information to get you started. You can also call them by phone and they will help you through the process. Their phone numbers can be found on their websites. My understanding is that a lot of people skirt the law and don't get business licenses and don't pay the sale's tax...but if they get caught, not only do they owe all the back taxes, but there is a huge penalty/fine. It sounds like you are trying to do it the correct way for your friend.