To Mortgage Other's Property
A debtor may mortgage some property, which does not belong to him, to a third party provided that the owner has authorized him to do so.
Deposit in Rent
It is not permissible to rent a house by only paying some deposit [i.e. without paying any rent]. However, there is no objection to renting a house and stipulating in the rent deed that the tenant pays a certain amount of money as deposit.