I previously owned a 140 year old home in southern newegland built by an old sea catain. the existing foundation was ledge and stone with a 2 foot crawl space. I started by jacking up the house and inspecting to see if it were worth while. then with kids (metal) sand shovels and a five gallon joint compound bucket, I began the big dig. I then graduated to a folding army shovel. I had people outside to haul the empty buckets for me. You will also need a place to unload the fill nearby (mine became a parking area after I was done with the house). Fortunately the stone walls went down 5' below grade. When I was done I put mortar between the stones and poured a floor and installed a sump pump. Then dug out by hand an outside bulk head entrance. It took all summer but was worth it to me. If you do it yourself and have the time its cheap. - Where there's a will there's a way!