Project specification is gathered and quote accepted, then 10% of project cost is paid/collected to start.
Project development is divided into milestones then development and testing commences.
Payment made per completed milestone. E.g.; 10% - Initiation, 20% - Planning & Wire-framing, 30% - UI/UX Design, 30% - Development & Testing , 10% - Project Delivery.
Project delivered, then update & maintenance service commences.