Authorized User Information

Can someone please give me a detailed report on the authorized user info? My Grandpa has a 832 Fico score for TU and a 822 for EQ and he has 2 CC accounts with $25,000 CL and like 30 years of ontime payments and he will put me as an authorized user if i show him information that it wont affect his credit and that i dont have to have a card to get the info reported to my CR. Can someone please get me a link to a proven website that can help me out. Thanks Michael