i ordered an 18 x 25 with 9' eaves, like one of those carports advertised everywhere, i did opt for a 4/12 pitch roof. made the level pad myself & put 6x6 treated posts around the perimeter (square & level) & filled with crusher run gravel.the 9' eave height alowwed for a 10' shed down both sides that i added when i could afford it. ended up with 900' enclosed. it took a little while as i did what i could afford.
the prefab shed was 2 grand. paid for it by hauling scrap metal, including my old work van that i drove for 20 years, to the Junk Monkey.(local recycling place)