Request Emirates ID, passport and residence visa (ideally 12+ months' validity), plus proof of employment and salary - a common guideline is income of at least three times the rent. With the tenant's consent you can pull an AECB credit check, and the RDC's Rental Status Sheet or Good Conduct record reveals any past rental disputes.
Rules and eligibility criteria change — confirm the current position with the relevant authority before acting. This is general information, not legal advice.