Do I have to pay a Deposit?

Yes. According to the Urban Leasing Law in Spain, it is necessary to leave an amount as deposit for the apartment.

Keep in mind that it is a guarantee for the owner in case the tenant causes any damage to the property during the stay. The amount of the deposit to be paid must be confirmed on the apartment of your choice, although in general it will not be more than the equivalent of two months rent on long stays.