... is between the fact that he doesn't want to do anything to help around the house and the fact that he's always begging for money. Pay him to clean up. He doesn't clean up, he doesn't get paid, and no borrowing allowed, no other source of income from the family.

Sounds like it's either that or make cleaning up be a stipulation to getting free rent (if he doesn't clean up he pays monthly), but that one's harsh and your parents would need to be willing to follow through on the threat if he ignored it.

Third option: dress in a fake space suit and wake him up in the middle of the night to scare him straight, a la Marty McFly in the first Back to the Future movie.