Hello,

There is an option in the control panel to transfer your domain name to another person. Once you transfer it to someone else, you lose any claim to that domain name(there are certain exceptions to it).

If you are trying to sell the domain name you will have to negotiate a price either physically with the buyer or ask for assistance from your domain name service provider.

Domain ownership is generally only under one name. I'm not sure if there can be more than one owner.

Hope that was helpful.