yep found the greenhouse frame on creigslist 350.00. yes we used coated wire 3 feet out around bottom and going to cover with 6-8inches of clay soil.
putting a 30x20 tarp across one end for weather protection. building the next ones above ground.
I'm looking forward to pictures of the above ground setup. I keep reading that those are best for the birds, but it seems like a PITA with respects to initially building it and catching them at some point.