Decide in writing what a qualified applicant looks like to you before you're looking at real people with real stories. Then apply it the same way to everyone.
What you're allowed to ask for and consider under Ontario Regulation 290/98: income information, credit checks, credit references, rental history, and guarantors — with one condition. Income information must be considered together with everything else you've collected, never on its own.
What isn't allowed: minimum-income rules and rent-to-income ratios — the informal "rent shouldn't exceed 30% of income" test — are specifically prohibited as a screening tool. And you cannot select or reject on Human Rights Code grounds, which include receipt of public assistance, family status (children), age, disability, race, ancestry, place of origin, religion, sex, sexual orientation, gender identity, and marital status.
What you can do is set a consistent, documented standard — credit history, verified income, reference checks, complete documentation — and hold every applicant to it equally.
Why this matters
Criteria written before you're emotionally invested keep every applicant measured the same way. That's the fair approach and the defensible one, and it's also how you avoid talking yourself into a weak file at week six of a vacancy.