Who's "first" for tenant priority?

[Therese V.]

I have an application, an application fee, and the background check. The background check requires the potential tenant's email address and it sends them an email asking to verify their information and ok my background check on them.

I have a potential tenant that came today and filled out the form, paid the fee, and I'm waiting on the potential tenant to ok the background check through their email. I just left a message on their voicemail letting them know they should have received the email and if not to call me back so I can make sure I typed the email correctly. 

I have an additional potential tenant who wants to pay the fee and has filled out the application.

How long do I wait for the other person to ok the email? Are they "first" in line or is there still room for "first" since they have not oked the background check through their email for the site to send me the report yet? 

What is the proper thing to do in this position?