You can get discount foam if you buy a tractor-trailer load of it. It seems to go for about half price that way. Foam type, thickness, and quality varies, but is stated ahead of time. If you can get several households together it might pay. Not free, but...
Dan
You'll never get away with this you overconfident blob! The most you will ever get is this tiny ad:
Homesteading and Permaculture Bundle - More than 35 Things