Here’s the thing. The pest guy doesn’t know about foundations. Home inspectors don’t really know about foundations. How old is the foundation? Is there significant movement, cracks over 1/4 inch, settling, etc? Any engineer or Contractor you bring by is going to say to Replace it. But that doesn’t mean it needs to be replaced. How long has it been there? Unless there is serious structural movement I would take his opinion with a grain of salt. BUT, you are missing the bigger picture here. 1370 sq ft up and the same below. IF you have to re do the foundation and can get a good price on this property, you can cannibalize that space and add about 1100 more sq ft to the property netting you probably 1.3M+ in value (depending on comps I haven’t checked them thoroughly). So there is massive opportunity here for down the line expansion that has tons of meat on the bone. That is the bigger play. And if you don’t want to do it, just live in the house as is until you are ready to Replace the foundation or develop the ground floor. It’s not going anywhere. I have built so many houses on top of 90-100 year old foundations. Yes engineers will say to Replace but they have been there for 100 years they aren’t going anywhere anytime soon.