2. I have also heard of people picking up seed totes second-hand, depending on your proximity to a seed cleaning house.
3. On the family farm, I have seen good 40 x 48's made into a box by adding sides and a lid, using 1/2" plywood. A little more work but very cost effective. Corners strengthened with 2X2 "posts" glued/screwed into place. The lids are great, keeping shop dust and the like OFF the parts.
Good luck to you!