i need a 24x30 here a couple years ago and looked at every option there was twice.haveing it built was going to cost double or more the materials, no way around it. i think id of been lucky to get it done for 6000$ if i hired someone.i looked at sum of those prefabs, they were all high.so i did what my penny pinchin german ass always does and built it myself.2x4x8 ft walls, cement floor, garage door i got at a yard sale, 2 windows i scrounged for freenice pre hung alum frame entry door i found at a auction for 80$.turned out really nice and i ended up with prob around 26-2700$ in it. one thing you might look for as i noticed yu said you had sum turkey houses.lots of poultry houses being torn down here and the metal trusses and lumber are dirt cheap compared to new stuff.they make sum pretty nice machinery sheds when from them round here.in fact im building a barn for my dad now 20x60 and we got everything to build it, except for the nails for aroun 2000$ or less.