The other two are still doing their due diligence, which may take 2-3 weeks (waiting on soil test results).

Did you have to get a soil test?  

They have the same soil type as my lot (“Alderwood gravelly sandy loam, 3 to 15% slopes).

A developer buys a property for X amount of dollars, and has to put in all the infrastructure to support the project (underground utilities, roads, curb, gutter, sidewalk, drainage, deal with any environmental concerns, soil stabilization issues, earthquake requirements, cost of a neighborhood park, contribute to a nearby traffic signal, etc. and many unforeseen things) ALL of these things add costs to a development.

They take out the old ones (2), remove some soil, and put in new ones.

Your FIL probably hadn't jumped into overalls and crawled underneath the house - any contractor that does and who has your interests in mind would be able to point out first signs of termites, mold, moisture and things like obvious cracks in foundation that old houses are famous for.

This model had the flame sensor underneath the gas flame bar.

The environmental cost of inorganic fertilizer is in 1) the mining of the chemicals, 2) inorganic chems can can kill microbial life and damage overall soil health, and 3) runoff from lawns and ag with chemicals affects nearby water quality.I've been an organic gardener for years and don't use any chemical pesticides on anything.

Something happened yesterday that might have an effect on the intown market: Part of I-85 collapsed due to a fire underneath.

Decades ago it was a radium factory and the EPA removed about 100,000 tons of soil which was radioactive.