Proper way to reject rental applications

[Sal M.]

I have received 3 applications for my rental property. I have completed tenant screening using houserie.com. And some googling. I have selected one out of the three and want to proceed with lease signing and security deposit collection. What is the proper way to notify the other two that they have not been selected and their app fee will not be refunded. I want to make sure i follow protocol to prevent any trouble. Do I have to provide a reason for rejection? These 3 applications came in during the past 4 days. Can I retain one of them as a backup, in case the selected one does not go through the next steps.