If he is paid under the table, he probably doesn't have a contract either. In the contract it should say what leave and workinghours is permitted.
Its very risky to work without one, as the employee is not protected by a contract then or the conditions of service.
According to the General Labour Law Act (not sure if thats what its called), any permanent employee is entitled to 15 days annual leave.
He should discuss his predicament with the companies' HR dept and if he is a member of a union he should seek their advice as well.
Im concerned as to what will happen if he should be in an accident while working the long hours...will he be cared for by the company or abandoned...