This is a common question and a topic that confuses some homeowners. Typical down payments are between 25% to 33% for large remodeling projects but can vary based on the type of job and what you negotiate. In general, you don't want to pay ahead of the work being done, but you have to cover the contractors costs to start the work. Always get the details in a written contract.
A down payment is almost always required when products have to be ordered by the contractor to complete the project. And some of those items have to be ordered far in advance….for example doors, cabinets and windows are usually ordered well before the construction starts. Then the contractor will most likely want you to divide the project into 3 or 4 equal payments so that he can continue to cover his costs.
Before hiring a contractor, make sure you are comfortable with the payment schedule. Discuss the details and ask the contractor to explain the process and requirements carefully.