Before you book, are you sure your property is legal? New regulations exist in Spain and these are designed to protect you. Make sure you book through a reputable agency. If you use one of the well known portals such as AirBnB you can usually be sure that they will have done some checks to make sure the property exists, and is legally available for rent.
Every property that is offered for private holiday rent in Spain must have a license. This license number must be displayed on any advertisement. You can check the license here. Enter the registration number and search, make sure the address of the property you want to rent matches the details on the register. This service is provided by the Government of Andalucia.