You guys would benefit financially by moving up there. I'm also assuming he would not be able to find a 16/hr job in SC? If he could find something comparable, why could his dad not help him from another state? Maybe not as much since he won't be working for him, but at least a little? So would his dad only be helping with the house/apt down payment if he moved up there..kinda seems trapping. Because if you guys bought a place, you're more likely to stay there longer? Is there a plan to move back? Is this just temporary to help get things started? Also working for family long term can cause issues.
I think if it's short term and it would benefit your future, it may not be a bad idea. But I would hope you and him have tried your best to see if financially you could also make it work in SC because OH sounds veryyy depressing. And you live in a really nice city so it had better be worth it.