Yes, you must sell both together to the same person, since the free V-Collection2 serial is linked to the Spark serial.
You are not allowed to un-bundle the free serial.
Once you find a buyer, please contact Arturia to request the transfer of registration of both serials from your account to his account.
You will also need to get a USB-eLicenser (aka Steinberg Key, ~$25) to transfer the V-Collection2 license from your computer to the the dongle, and include that activated dongle with the Spark+VC2 bundle so the new owner can use the V-Collection.
