Tenant selection sits at the exact point where good business judgement and anti-discrimination law collide. Get the process wrong and you expose your agency to a tribunal complaint before the tenancy has even started.
The lawful question test
Every question on an application form, and every question you ask verbally, should pass one test: does it relate directly to the applicant's ability to pay rent and look after the property? “What's your income and employment status?” passes. “Do you have children?” does not — family or parental status is a protected attribute in every state and territory. If you wouldn't ask it of every applicant regardless of their background, don't ask it at all, and don't let a landlord ask it through you.
Write your intake script once and use it verbatim for every applicant: employment and income verification, previous rental history with contactable referees, identification, and any pet or occupancy details relevant to the property itself (number of intended occupants, not who they are). Consistency is your defence. If Applicant A is asked about their visa status and Applicant B is not, you have created a pattern a tribunal will notice, even if no one intended harm.