1. will his bad credit affect mine negatively if i make him an AU on one or both of my cards ive had for a while or one of my new cards?No.
2. the 2 cards ive had for almost 2 years are Credit One Bank and Cap1...do they allow you to add an AU?I don't know. Call them and ask.
3. my new cards is Hooters MC and Chase Student MC...do they allow me to add an AU???I don't know. Call them and ask.
4. How long do i have to keep him on there before it starts reporting on his credit?When you add him as AU, it should report for him as soon as the card reports on its normal monthly schedule, which could be up to 30 days. If it doesn't the first time, then it likely will the second time. So it could be up to 60 days or so.
5. What happens after I take him off?The account will be removed from his report.
6. How much will this help him?Too many variables to answer this. It depends on the history of the cards being added, how old they are, what the current reported utilization is on them, etc etc.They probably won't help much. Adding new positive accounts is a good way to dilute bad history when that bad history is very old, but he is still going to have recent lates, which are going to hurt him for some time to come no matter how many new positive accounts he adds.Also, he's going to be dinged for new accounts if you add any that are less than 12 months old. Your AU accounts may also lower his average age, which could hurt.There's really no way to give a good answer without much more information.