One of the very first questions that should get asked right up front is "Who is paying for the project?".
If this is an internal project then it may be a special budget, or a specific department or multiple budgets or departments.
If it is a customer external to the organization it is best to qualify them to see if they are willing to pay x dollars for projects and check their payment history.
The last thing you want to do is a lot of leg work only to find out the customer never had any intention of buying or they did not realize the scope of the project that they were asking for or there is no budget or funding for the project.