What is the ruling on mortgaging a house for a sum of money, with the mortgagee living in it for a specified period, then the money and the house are returned? Is this considered usury, i.e., "a loan that draws a benefit"?

The mortgagee is not permitted to benefit from the mortgaged dwelling in the manner mentioned in the question. The scholars have reached a consensus on this, because it falls under the category of a loan that draws a benefit, which is forbidden usury (riba).

If the benefit is in exchange for a fair market rent, the majority of scholars hold that this is impermissible, though the Hanbalis permitted it. The safer course of action is to adopt the view of the majority.