Unless there is something that changed, if you can prove you asked the same questions to every single applicant, it might not be unlawful. But, you have to prove you've asked every one. And then there are other factors, such as, is this rental unit owner occupied, under a certain number of units, etc. Definately needs to check the local laws though.
I own apartment buildings and follow the city codes to a T. The people who live in these buildings lead their lives and pay their rent and are good tenants. My attached apartment needs a married couple or a contintint single because I have a pack of kids as well as my own values to consider.