What do You Get in the End and How Long will it Take?
As good as possible clarification is needed on which product should be developed and how before starting the development. From this one can plan what is the size of the investment and how long the development will take.
Already in the first development phase we keep an eye on the whole life cycle (design for test, design for manufacturing, design for cost) in addition to non-functional requirements like safety, usability, maintainability. So expensive revisions can be avoided in the later development phases.