Make his life a misery, for the rest of it.
As Mr Robbo says, they'll probably try professional debt collectors first. If he won't pay them, they could get a court judgement, which will give them the right to enter the house and take goods to the value of the debt. If you don't own enough to cover it, you could then lose the house (if you own/mortgage it).
And after all that, he will also get all this palaver recorded on his credit record, so that he will be unable to get credit again. No credit cards, no HP, no loans, no mortage.
Does he think it's worth it?
If he is unable to pay, then start talking to them, and explain this. And/or get debt counselling.