You probably already have many of the basics. Other items you will need and may not have include presentation folders for proposals and final reports, shipping supplies, and mailing labels. You'll need materials to stay organized - file folders, hanging folders, a filing cabinet, etc. If tidiness and organization are not your strong suits, find someone who is good at that and have them help set your office up for you. Being able to put your hands on documents you need when a clients calls you unexpectedly will reduce your stress level and reinforce your image as someone who works efficiently.