If FL is a state that lets the buyer have the license plate or you just take the plate, you should be OK. No plate or paper plate, not good. Plan B, have the seller get a 3 day or whatever FL has, slap it on good and go. At least you would be doing the best you could. MAKE SURE you have the title and bill of sale with you. The phone number and name of seller so if a cop wants to call they can. Get insurance ahead of time and make sure it has towing.