Elk that is a valid point about maybe not getting what you might have in the barn when you sell it. When we sold our house in Connecticut with a barn. We received no more money than houses like it were selling for. It was a high quality Morton building with extras and was a pleasure to look at and work in. It sat well on the 3 1/2 acre lot and looked good. I enjoyed the heck out of it and it was worth having had it built.
It was a factor in selling the house but it didn't add to the sale price (kinda like what I hear swimming pools are like). Still If I were to build another barn it would be just like the three we have built so far but with the addition of a ten ft. lean-to on each length instead of one length. We have 12 ft. walls, 1 inch thermatex on roof with seams TAPED under the steel, 1/2 inch thermatex with seams taped on all walls, two ft. overhang with gutters, insulated 12 ft. wide over head doors, two pass doors and plywood all around the lower four ft. inside the barn sitting on six inches of concrete with thick plastic and insulation board underneath it. I put Pex in the concrete for heat and electricity of course is a must. Winters are long here so 64 ft. was the minimum length ;it allowed a twenty yard bow shot on snow days.
Its money you don't necessarily get back but it makes being in there great. Note--in Connecticut the insulation was because you couldn't stand being in them in the summer without it --too hot plus roofs "rained" inside. In New York--same reason plus a start at insulating for the cold and preventing icicles in the winter which would take gutters down.
So the first thing in building a barn is defining your absolute criteria for having it. The cost can run from twenty to seventy-five thousand or more for a 42 by 64 plus lean-to's depending on what you are looking for.
I'm with you Catscratch on the trailer boxes--I don't want to see something like that every day regardless of the low cost. As a very temporary deal though it would be fine but no not as a permanent structure. For you Catscratch I understand how you would weld outside so a hot building may not be a big deal. However as time goes by your use of the building may change and doing it over usually doesn't produce as great a building. Everything changes overtime.