Most people of the working class earned just enough to stay alive; they could easily been thrown into poverty by illness, layoffs or even a sudden misfortune that could have caused a short-term employment. People in unskilled and semiskilled jobs generally needed more income from other members of the family. Since manual labor was as demanding as it was, working men were often most highly paid in their twenties because at their peak physically. At this age, they married and for a year or two, husband and wife continued to work and there was even a little money for a few extra things. But upon the arrival of children, a woman could not continue to work a twelve to fourteen hour day. She might have earnings at home where she did piecework or took in a lodger. The family would be quite poor, while the children were small.
As the man grew older, he earned less as a result of his diminishing physical condition. Girls and boys had to start working at a very young age. They had very little schooling and even before they were old enough to have regular jobs, they often helped in the same work done by older members of the family. Once the children were all working, the family could temporarily rise above the poverty level. The parents might be able to accumulate a little savings for their own households after all of the children were married. At that stage of the parents' lives, poor food and hard labor had weakened their health. They could not earn nearly as much as when they were younger. If they lived to be old, they would more than likely be very poor and return to poverty status. Their days in the workhouse would end if their children could afford to take care of them.
Mitchell, Sally. Daily Life in Victorian England. Connecticut: Greenwood Press, 1996.
From http://www.cwrl.utexas.edu/~scoggins/316british/WutheringHeights/lower.html