This is a common problem here in Texas. There is a company called Ram Jack that does a very good job in this area. he charges $500 per jack, thats material and labor. he digs a huge hole under the foundation every 20 feet aound the perimeter of the foundation. At the bottom of this hole he pours about 2 feet of concrete. On this footing he will istall a heavy jack and jack the home up at each hole. When level, he just pours in concrete with the jacks in place and walla.