I have a foundation that has settled around 3" on the back corner of the house that I am trying to flip. We are building a retaining wall and going to underpin the foundation with concrete piers. My issue that I am having is I have been quoted 5 to 16 piers from 4 different contractors.

I have decided to have a structural engineer come out and give me a structural report to determine what he thinks needs to be done and build based upon his findings.

My issues that I am having is that I have a contractor who claims the house only needs 5 piers and is at $3200 and provides a 'Lifetime Warranty'. If there are structural issues in the future does the liability fall on me or the contractor who installed the 5 piers? What if he goes out of business, dies or otherwise would this lifetime warranty be worthless? Would I be liable for the foundation repairs, or does it matter as long as it is disclosed with the sales contract?

Any thoughts on what I should do here? Will I have any issues selling the house if I just get the 5 piers done by the contractor with the lifetime warranty or do I need to have a structural engineers drawing and approval to attach to the sales contract?

Thanks for your help!