We have bought some shipping containers from Mayflower Movers in the past for around $45. They were plenty big enough for two people to sit in. We reinforced the floor and you have to cut windows and a door in them. I am not sure if they still sell them but it is worth a call. I attached a pic of our porta-potty stand just for kicks, glad to see we are not the only ones.
found this on craigslist- ocala
Hunting Blind - $495
Hunting blind deer stand
New hunting Stand blind with panoramic gun ports
7 1/2' tall
Door is 41" wide and 6' high
Pressure treated 2x4 framed plywood floor
T-111 siding and galvalume metal roof
Fits in the back of most pickup trucks
$495
Watch the video below on how this blind is built
http://www.buildyourown-huntingblind.com
check out redneckblinds.com
Not mine just saw it. looks like it was built for shooting out of. hay hut - $475 (dunnellon) 
