You have it right a business or tax number gives a lot better buying power. I had all that at one time. As soon as I did away with it and pay the sales tax when I buy parts with cash things change. Yes I do get a small discount but its not whole sale but closer to retail. This is all OK with me because its not a full time business and I don't pay any taxes. I charge more for parts and less on labor. After a job the money go's in my pocket with no paper trail. No signs or advertising, word of mouth only. Its a retirement thing nothing more. Just how do you think I have all this time to be on this forum, its sure not working in my shop.