I have a real business with a real tax ID but I already got both Inks a month ago using that so this time I was trying for the sole proprietorship of which I dont really do anything...
I am no expert, but I don’t see why you can’t send in the info from one of your legit businesses and say you need a 2nd card for that business to separate, organize etc expenses (unless that business is not registered to you, because then it would be hard to explain why you used your ss#) from 1 yid to another- hatzlacha