Planning to build a new home, but figuring ways to do it on the cheap. One biggie: Knew I was going to go with earthbag walls but was unsure on foundation--monolithic slab would run over $10,000, and even a four inch slab would cost $4300 at present prices.
Current (and going to happen) plan: Concrete BLOCKS (not poured in place, so no contractor) for perimeter only, cost under $500. Floor to be natural Earth, with ONLY (a) a 6 mil plastic sheet ($72) topped with 1/4 inch rubber flooring ($1475). Very "resilient", save wife broken bones from falls (her balance is not good), improves thermal mass.
Bottom line: Complete foundation plus finished floor will come to $500 plus $72 plus $1475 = $2,047, versus what could have been over $10,000 with floor not even included.