Federal job offer but scared about the credit check?

Someone that I know has been offered a federal job but now they mention they will do background check and credit check. This young man owns a home which he has pay monthly on time and doesn't have credit card debts. His current job is getting ready to lay him off and he has 1000 worth of debt for medical bills due to a horrible injury. He has had a case of misfortune things happening and haven't had the money to pay off the bill yet. Just now he was offered this job and things are looking up, however he is extremely concern about his credit which is 600 ish. I would like to hear from people who have experience with this or who work in the federal field. Not folks who just talking out of their behind. Thank you