So, I'm at that point of life. Scary, I know, but I was hoping to get some advice... Do I just add him to my account? He is 18 and I want to help him build his credit, but obviously don't want him to hurt mine? Suggestions? 

My mom did this with my brother and it went well except he went to apply for a loan to get a new car and was denied because the card (which she primarily used) was pretty much maxed out. Lol She didn't know that it affected him as well. She paid it off and then he was fine and able to get his loan. 

From my understanding, there's a difference between being an authorized user and a co-owner. Co-owner would require his credit to be approved. Authorized user doesn't. I think u can ask the credit card company to make him an authorized user for a smaller credit limit on your card. For instance, if you have an 8k credit limit, you might only allow him access to $300 (a common starting credit limit).

Another option is to have him apply for his own card. If he's never had credit before there's a lot of major cards that will approve him at the drop of a hat because they want those young'ns hooked on credit early (unfortunately). They usually have MUCH higher interest rates, though.

Finally, there's also the secured card option. This is where you pretty much put $300+ on a credit account and they use it like a "Credit card." They have to pay off what they use and it helps build their credit. I think after about a year on that account, if the account has been handled well they refund u the $300 and it turns into a regular credit account.

...can you tell I used to work for a bank? ;)