Paul has a good answer below. From a lender's standpoint, we get questions from contractors asking if they can be approved by us in advance. The answer at Wells Fargo is that we don't submit contractors for acceptance until we have a loan in process and the customer has selected them to handle their project.
The process to allow a particular contractor to be accepted by Wells only takes about 3-4 business days as long as the forms are filled out properly. As long as the contractor is a full time builder and is licensed and insured with good references, there are typically no issues.
Once a contractor has been accepted by Wells, they are able to do additional projects with limited paperwork as long as their work is satisfactory. Good luck with your project.