I went with prefab because of the time it would have taken to build a similar pen with me trying to source the material and the time it would have taken to cut and weld the pieces together.

Plus I can still disassemble and move if i need to.It is also expandable by adding another pen and bolting together. Hey, if Boss of the swamp can get by with not knowing how to mechanic, I can buy a prefab pen even if i know how to build one.

That 1/4" impact driver is a worthy tool to have if you do any building and assembly. I just happen to have dewalt, other brands work just as well. Probably the best tool you could have for putting sheet iron on a roof without dragging extension cords around. Works much better than a plain drill with bits.