I've been involved in 2 of these projects.
20 years ago: This involved a skidsteer, jackhammer and a single weekend worth of work. We dug a ramp to the frost wall, jackhammered an 8' opening to get the skidsteer under the house, and dug like heck because we only did a 2 day rental. We hit a stone easily 6' in diameter, we dug around it and were able to reach it with a full sized backhoe for removal.
10 years ago: The second project was helping a friend with a 200 year old house and involved 5 gallon buckets, a wheelbarrow and shovels. I helped a few days over the 6+ months it took him to dig out the basement. He never hit a rock bigger than your fist.
The only way I'd do it today - hire it out.