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.
Similar fossils have been previously interpreted as bacteria, fungi, single-celled eukaryotes, green algae, and various types of early animal life (including transitional forms of modern animals, relatives of sponges, sea anemones, or bilaterally symmetrical animals).