Does the place he's renting accept credit cards as a form of payment? If so, you're really lucky! If not, you'll need to use a rent-payment service to pay it with the credit card and pay a fee, usually around 3% of the cost (which is worth it if it means getting large amounts of bonus miles you wouldn't otherwise be able to get).

Do not use a cash advance to get the money to pay it, as the fees will be higher and you won't get points.