Try This. . .
I've heard of some people using card board boxes just layed flat on top of each other until you get it to the height that you want. And you can get them from a grocerie store they throw tons of card board out. Once you get it high enough, put some stakes by the corners so nothing can move. Then go get a big hammer and go to the hardware store and buy the biggest Nail you can find, get 4! . . .(bringing the hammer with you is optional) Nail the four corners and this will last forever you can cover it with a tarp but because everything gets so tightly packs together the water doesn't seem to hurt it real bad but snow and ice will. Then just buy a bulk pack of paper targets or whatever you want to shoot and pin them up there.