Questions about rental processing

[Yan Guo]

I just did the first time handling the application process by myself. I was kind of nervous and excited. During the process, I have had some questions that I never thought about. If I received multiple applications and all of them have paid the non-refundable application fee for the credit report and background check. If I found out from their current landlords that they are not as good as they said themselves. If I am going to reject them based on this, do I still need to check the credit and background? Or I can keep the application fee without pulling the credit? Or refund the money back? I had done all the credit and background chech no matter other factors are good or bad. I am wondering if it is really needed? Thanks.