Generally a rental list is supplied for a single use only. Rental means you do not own the list, but have the right to use it once. Any responses become your contacts and can be added to your own database. Some lists can be rented for multiple uses where second or subsequent uses are provided at a discounted rate.
 
If a list is available for purchase, the Datacard will usually indicate a Purchase rate per 1,000. When a list is purchased outright it can be used repeatedly.