For a basic 500 square feet project in zip code 47474, the benchmark cost to Insulate Your Home ranges between $0.63 - $1.43 per square foot* . To estimate costs for your project: 1.
So in answer to your question, the oldest fossils are stromatolites, and the life forms that created those fossils were prokaryotic bacteria and algae like cyanobacteria.
Life arose from this life-less but churning mess sometime during the first several hundred million years of Earth's existence, but the details are inaccessible. The oldest trace of life may be a chemofossil from a 3.8 billion year old rock in Greenland.