An applicant with any collection that has or has not been paid should be advised of the following.

Collection amounts that have been satisfied will not directly affect your application with the exception of how they may affect your reported credit score and if rent related, what the landlord with the collection reports in a verification.

If the collection amount is unpaid, it likely is seriously impacting your credit report. Whether or not you believe it is justified, it likely will be an issue with the overall ability to approve an application.

For a clearer understanding of the application process please refer to this article.