@Shane Clark
Shane, I feel your pain! hahah. I was looking for properties over the last few months in the Lowell/Chelmsford area and in my price range was only 1900-1940's houses with fieldstone foundations. I just bought a SFH in Chelmsford with a fieldstone foundation, and it was in great shape and was pointed really well. Doesn't scare me at all. Here is my $.02:
1. Don't be afraid of a fieldstone foundation. They are structurally fine and can last 100's of years. (although don't ask a structural engineer that they will tell you they have no idea how the house even even standing!) Engineers.....
2. What you want to look for in a stone foundation is bowing in the wall, the plumbness of the wall, cracking or displacement of the stones, or sand at the bottom of the wall.
3. Sand at the bottom of the wall will indicate that the mortar is breaking down. If this is the case, a foundation can easily be repointed and there is a plethora of companies out there that do it. When I was looking at pricing I was looking at between $5,000 - $8,000 to repoint the whole foundation. Mortar breaks down over time, it is what is is. If someone has repointed the wall recently you should be fine for another 50 - 100 years if it was maintained correctly.
4. Even if the wall is crumbling down in parts, it's just another day at the office for these guys that fix them for a living. No matter how scary it looks, it can be fixed. Probably looking at $10,000-$20,000 to fix isolated areas that are crumbling (and I mean crumbling), or about $30,000 or fix the whole foundation. They will support the load of the house and go underneath and relay the stones.
5. I have also looked at prices to raise the whole house and pour a concrete foundation. Probably looking around $40,000 to do this. Although, the president of my company who has a mason background, jacked up his house himself and put in a CMU foundation and was all in for $5,000. So it depends how much skill you have.
6. Your going to want to look at the floors above, and obvious sloping of the floors. This may indicate a foundation problem, but it could also be from undersized beams and floor joists.
7. I talked to a guy named Andrew that owns a business in NH called The Mended Wall. He had a lot of good information for me and he knows the business really well. Can look at his website for past projects. I've never used him or even know him from a hole in the wall (no pun intended) but he seemed smart. I also looked at Done Right Services.
8. If there are no obvious defects, I wouldn't be too concerned. The house won't be falling down anytime soon. This is what you have your inspection period for anyway. For $150 they will come out there and review what needs to be fixed and give you a price. Money well spent to know what your in for.
I kind of rambled on here, but the main point is don't be afraid, be educated. People look at crumbling foundations and get scared away before they even educate themselves. It's good for me because it leaves more opportunity for me.
Hope this helps.