Let's calculate the steel reinforcement now. Assuming spread footings on the centerline of each bearing wall with eccentrically loaded footings on the zero lot lines. Let's calculate a soil bearing strength of 2,500 psi and oversize our footings to 10' wide, 32" deep with #5 continous at 8" oc each way, top and bottom. I show +- 600 #5 bars @ 20'.
Let's cast every single interior and exterior wall with #5 @ 8" oc Horizontal and 12" oc vertical. I show +- 1,200 #5 bars @ 20' That's a 100% cast concrete floor, walls and roof Alys Beach residence using an oversized 1,800 20' rebar at over paying $8.50 per bar makes $15,300 for steel. Correct my math with your theoretical Alys Beach concrete residence. I'll wait