solfware ownership

I have a client who has a new comcept and is requesting a large prime IT deve. to furnish a price on “work for hire” The IT co. has already dev. some item that can be used within this new comcept. Q – when my client pays in full for the system who own it? and/or how can client keep IT Co. for marketing the systems nationwide. an/or receive payment if they do market with an agreement. If so, anyone have such an agreement?
Thanks for any help. Rooster