When you pick up the car a credit card (and not a debit card!) on the name of the main driver is required.
Rental companies want a deposit, which means they block an amount to be sure you pay when you return the car with damage, when the car is returned late or when they receive a speeding fine after you returned the car.
Which amount they block differs per rental company and per location (check the rental conditions for the car you want to rent). Even if you have an excess insurance they will often block the amount of your own risk: in case of any damage your insurance will refund that to you afterwards.
Without a valid credit card on the name of the main driver you will be refused a vehicle!