The hardest part at the start of a project is to clearly understand what is needed, what is nice to have and define what can't be included at this time.
The only path to that project definition is to ask leading questions and LISTEN.
Time must be allotted for questions, research to answer those questions and develop new questions for develop an optimal solution. This stage of project outline development is critical and despite best efforts on all typically never matches the final delivered project.
Budget definition and at times an adjustment results from this process. We often recommend a staged implementation to segments of a project in order match costs to cash flow.