I had a 40x50 Steel building built about four years ago, contracted to a guy who had a great reputation in the DFW metro area, (actually outside the metro area a few miles in Weatherford) who custom ordered steel purlins, girders, uprights, etc. and welded it all together. I had it wrapped in white insulation, and color choice of exterior walls and roof, plus two 15 ft. long roof vents that ran along the spine of the roof. I had two doors installed in front, one 12x12, and one 9x12 in order to drive RV inside, along with space to store enclosed trailer and a couple of race cars. I installed cabinets, sink, hot/cold water, and 200 amp electrical service myself, making certain I ample 120 outlets, a 50 Amp for the RV, both inside and out, and a couple of 220s for the air compressor and other power needs. He used 6 inch concrete for the base flooring, including a 25x40 concrete apron. Also used a 12x12 door for the rear, thinking I could drive the RV through and into the back yard. Unfortunately, I was unable to use it due to not having enough space to turn the RV prior to the fence which was only 35 feet away. It was not heated or airconditioned, but I did have a 40 inch fan I used to push the air, and never needed any heat to speak of. Bottom line, this building was as sturdy as the brick house in front of it, tight as a drum, cheaper electrical bills than imagined, and a wonderful place to hide out and work on the two race cars, clean the RV and trailer, etc... Cost without work I did myself was just over 30K, which included doors and power door openers for the two front doors. I had one walk-through door and one window, but plenty of lighting that seemed really bright with the exposed white ceiling/wall insulation. Counting material and my labor for water, electrical, and other necessities, one could add 5K, and still have less than 40K in this 2000 sq. ft. structure...
Unfortunately, my spouse retired from Verizon and decided we needed to return to KY after 11 years to be closer to her ailing parents...I couldn't argue with her logic, so I reluctantly put the place up for sale and promptly sold it, although with some regret on my part. If I were to build another building, it would be of the same type and material. I can't say enough positive things about my steel building experience...