As far as I understood, Retainer Contract is signed only when a client does not need you any more, but he wants to reserve a portion of your monthly time. so he pays for the reservation.
Is there a contract which my existing client and I can sign so that he pays me that I take his new project in work immediately? If yes, what is its name and what are the rules there?
I am asking as it makes no sense (looking from client's perspective) to pay me 80 hours a month via Retainer just so that I can work on his project immediately if he sends it in 4 months.