Typically, we follow one of three models, depending on the scope and nature of the project:
Fixed product spec, defined timespan: our primary role is developing the application and ensuring user acceptance.
Ongoing maintenance: this can be for a product we have developed for a client, or for a system that the client already has, and needs help maintaining and/or extending.
Idea to MVP and/or MVP to market share metric, flexible timespan: we have significant experience implementing innovative products in a variety of industries (supply chain solutions, music licensing, social music collaboration, vehicle leasing, staffing, etc.).