You can't really do anything to ensure that he gets the visitor's visa. It is up to him to apply for it and to better his chances of getting it he would need to provide documentation of his ties to Afghanistan ensuring his return. So any evidence of job, property, business, taking care of family will be helpful but still not a guarantee. From your end you can only assist in providing him with an affidavit of support showing that he will not need to work while in the US and that you will provide room and board for him.
Answered on Jul 27th, 2015 at 1:51 PM