from the very little I know it should help as much as being the primary cardholder does... and.. hurt the same if it is ever late..
I agree with Cibomatto. In my experience, scoring algorithms don't differentiate between AU and primary cardholder. I'm actually wondering if the reports creditors get include that information. It seems like they would consider it when doing a manual review, but no one has ever mentioned it. A couple of months ago, all of the positive revolving accounts I had were AU accounts and I still had no trouble getting a few cards.
Hmmm I am dying to know if my Platinum card in which my hubby is an AU will raise his score significantly. The account is too new to even be on our reports. His scores now are 606 Equifax, 619 Experian and TU not sure. But I hope it gets reported to all three CB's. Does that matter?