Using the best of both

To use the best of both approaches, you can have an initial getting the requirements phase, but with less detail than in the Waterfall approach. In this first phase, the requirements of all the areas are covered, so it helps the partner team to make an approximate estimation of the project cost and time. This helps the customer identify if the project fits their needs and also their budget. After that you loop through all the phases focusing on a few requirements at a time.

Of course, using this approach, the cost of the project is only an approximation; it may cost less or more.

If the project is finished with less cost than estimated, both the customer and the partner win, because they share the benefits of the savings. On the other hand, if the project costs more than expected, both have to share the cost overrun. This can be achieved by returning part of the savings to the customer, and compromising on the cost of the underestimated projects.

This kind of...