depends on a lot - is the property currently rented? for how much and how long? proof of payments made? is it on your tax return? does the borrower have experience managing rental properties? stuff like that ... in general if you are buying a rental property or if you are buying a new residence and renting out your old - you will need a full executed 12 lease with security deposit in hand prior to closing (and not renting to a relative of yours btw...) and we would use 75% of the rent as income to offset the expenses (ins, tax, hoa, mortgage payment) .. the net # there would be income or loss depending on + or -..
let me know if I can help you