Are you looking at leasing some IP addresses for your ISP or company? If so, check out ARIN’s page on IP leasing.
The biggest thing ISPs should pay attention to the following:
Address space leased without providing Internet services cannot be used for justification when requesting IPv4 addresses from the Waiting List (4.1.8) or specified market transfers (8.3 and 8.4 recipients). If you are leasing addresses to an organization, you cannot use the leasing arrangement as a reason for requesting additional IPv4 addresses.