As a client, you might think web design comprises things like a homepage and a few interior page layouts, but web design is so much more.
This is why a creative session is important for you so you can map out all of the elements, pages, and items you might need for your project. A thoughtful and well-defined creative brief will help prevent scope creep, make your project run smoothly, and set expectations upfront.
A good brief will also help you understand the skills and experience level you need, which should also help you with defining your budget.