I am planning on starting a business that deals with both local and internet sales of cool parts for bass and guitar by various companies, as well as eventually turning out some partially-custom products. Most of these companies will require some proof of business so that I can start an account with them. What do I need to declare to them "I am a business"? Where do I get it? What does it cost? I hope there are some accountants or sole proprietors here that can answer this.