see if the local high school/ community college has a welding class. have them weld you up 4x4x4 frame out of angle with one end open. Then get the 19buck fence panels from tractor supply. and wrap on the inside of the three sides. you can use hose clamps to secure to the corner angle posts. Then find some rail road ties or 4x4 or 6x6 or something and bolt them on the bottom as skids. These will last years and years. The pallets won't last and then you will have busted ones and nails etc laying around. 1/8th inch by 2 or 3 inches steel angle sticks are not much money and if the labor is free you won't have a lot of money in them and they will last you 8-10 years