I just completed a 40x50 shop next to a home we gutted and totally remodeled at the same time. Here's what worked for me. I shopped 5 different pole barn builders, (including Menards). The prices for what I wanted came back wildly different, so glad I shopped. I choose the lowest and started looking at references. The one I liked was 125 miles away but had done several in my area, and everyone gave great recommendations. They helped me with options, door and window choices and several suggestions including using some sort of plastic sleeve to bury the posts in my clay soil. They even found room in my limited budget to add a nice-looking cupulo.
I had a local contractor use a medium-sized bulldozer to level and prepare the pad on my hilltop. The materials were delivered and their crew showed up shortly. These guys were great! Wonderful craftsmen. They used a lot of screws but backed up everything with nails. Very accommodating such as moving already installed windows when I realized they didn't suit me. The crew was all Mexican and the leader lived about 2 miles from me and had built barns for over 30 years!
After it was framed, they were glad to start another job and promised to come back when I was ready for siding.
My builder son-in-law and I prepared and formed for concrete, but hired a finisher that could do this size job quickly. Without the siding, the concrete truck had good access to all the building without pumping. I did a 5-inch floor, but no rebar. We used fiber in the concrete instead.
The crew came back and did the siding and roof in one day. Several people encouraged me to add a 12' ceiling at the last minute, and the same crew installed it after I bought the metal.
Before insulating I did all the wiring and the plumbing for 3 hose outlets and a small kitchen. No bath... In our area, a bath triggers all kinds of permits, inspectors and more taxes. We put in 100 amp from the house 200 amp box, about 40' of underground (I will be working alone with no more than 1 machine at a time).
The insulator put spray foam on the walls and bat insulation above the ceiling. The ceiling and insulation were great decisions. I can heat the whole thing with a 50,000 BTU natural gas or propane wall heater. I am surprised that one old 5,000 BTU window AC kept it below 85 during a very hot Kentucky summer.
At a low cost, I included a 12' shed across the back. Lots of added storage for the money, but it was so nice, I am using about 1/3 of it for a patio where we grill and watch the sunset over the farm from our hilltop site.