If you have a Menards store near you, you can go to their "building" department. You tell them exactly what you want, and they can bring it up on their computer. They will offer different grades of materials as well as any option you want. I'm talkin' sky lights, vents, guage of steel, sizes & types of doors, etc, etc, etc. They will print off a copy for you to keep with no obligation, and you can always go back to Menards & tweak the design as you see fit. Menards will also provide a list of local contractors who can do whatever parts of the construction you want. BTW these contractors are "graded" by Menards using feedback from customers who have used them.
1) Build it bigger than what you think you need.
2) Consider a "man cave" section for you & the guys to hang out. (this also comes in handy when you want to get away from the wife, or have friends over)
3) You will have to submit a building permit (dimensions of building & your property, etc), but most contractors will be able to do this for you at an additional charge.
my 2 cents - Good investment, Best of luck