My Grandmother is in her 70's and has been with AMEX for about 30+ Years with only one recent late payment a few months ago. Also this is a AMEX gold so its basically a "charge card" that must be paid in full every month. She added me as an AU on her card today after I explained my situation. How much do you think this charge card could help my score?
It won't help at all with that late. And Amex will reflect you as a member since 2019.