We just really think it's an important part of the initial communications, to ensure that both service provider and client have a solid foundation for understanding. It really does help avoid issues later - especially when it comes to billing.
It's equally important to ensure that you have a good sense of what your client *expects* and work to clarify anything that isn't immediately clear.
Of course, some things are unpredictable, but these suggestions are a good start to setting up the framework for good working relationships.

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