Federal regulations govern the amount that a disability receives when a person is due back pay. It is usually the case that a person waits at least a year and a half on average before they even see a judge. If you are due disability benefits, then you will probably be due back pay because you have waited so long to receive your benefits. If there are back benefits, attorneys generally charge 25% of any back benefits, with a top limit if the case is won at the first hearing. There are some cases where there will be no back benefits, in which case most private attorneys must charge something at the beginning of the case. In many parts of the country, legal aid will help you with this sort of case.