How can we help this guy come back to his senses?

My neighbor's son is 23, by the way, he asked me to post this question... He wants to marry a woman who is 29... My neighbor and I have been talking with the kid for weeks trying to talk him out of marriage with her. First of all, she will never look at him as the authority or head of the household... and second, she will not be able to work as hard around the house when he is 55 as a more fresh 45 year-old would, for instance... What can we do to save this naive youngster?