Habitat for Humanity has what they call "ReStore" ... oh.mi.gosh ... I hope your area has one. J'adore ReStore! They get a lot of things, complete kitchens, designer furniture, bolts of upholstery fabric, oops paint, discontinued items from big box stores and items from deconstruction is one of those. Last weekend, our ReStore had old blocks for 25 and 50 cents each. Look for a ReStore or something similar. Also, when people tear out their concrete, or city's remove sidewalks. You can make a very cool habitat with broken concrete pieces stacked up. You may have to buy the lips at Home Depot but broken concrete is usually FREE for the taking. Where there's a will, there's a way. Check craigslist, too. Free section and farm and garden sections. Woo yaaa!