If you have an old house with old wiring, how do you know if repairs are necessary? How extensively and costly can such repairs be?

Electrical systems age and deteriorate just like any man-made product, and as they get older need to be monitored more frequently. As homes grow in their dependence on electricity with the addition of rooms, appliances large and small, and entertainment and computer equipment, electrical systems designed to handle lower electrical demands expected at an earlier point in time can be-come overburdened and problems can develop.