Yes.By rent agreement, do you mean from the tenant perspective? Yes, they are living on rent and can ask the owner to prepare rent agreement ( they will be paying for 2 months in advance as their rent before coming here).
They must include the rent agreement + 2-3 months' rent receipts + bank statements that confirm rents are paid
It would help your parents' TRVs if you share more details about their situations, etc. Otherwise it is difficult to advise