busi·ness [biz-nis] n. An economically active adult.
Seriously, you don’t need to overthink it. If you can responsibly handle and manage a personal credit card, you can do just fine with a business credit or charge card. If you’re really worried about it, pick up a good deal like Big Habitat does, sell it on Amazon and voila! Your own business, complete with a name and all. Generally, you do not need any kind of EIN or other anything. Most businesses are sole proprietors and simply use the owner’s Social Security number. Feel free to join them if the best next rewards card for your needs happens to be a business card.