Some questions I would want to answer: Has anything changed in the surrounding soil recently? 

Beyond the bedrock issue, soil conditions can be costly if the property has problematic soils such as too much silt, deep topsoil, or extensive wetlands.You'll also want to know what ordinances are going to affect your budget - things like tap fees, tree ordinances, storm water retention policies, etc.Bottom line is that you have to investigate ordinances, off-site conditions, and on-site conditions before you can even begin to budget your development.

Looks like you guys have a lot of port silt loam, which is NOT a very expansive soil.

They run my soil tests for me.

The soil composition had to be tested and cleared before development could begin.

Sandy Malega would be your gal for the Mid-Del area. 

Sometimes a sewage line will sag over time due to settling of the surrounding soil.

Typically with houses of this age - you'll need structural folks to dig and install piers into the soil.

Going over maps of known repairs with contractors showed that there were a few houses where people tried to have piers installed and ran out of money before hitting stable soil, others in the hyper local area did have to go to 100+ ft.  

If your house is not build on soil like that, but instead is built on more stable soil types, you probably will have fewer issues as long as the foundation was built properly to begin with.