We built a 30 x 60, every thing is on 10 ft, alley down the middle. Roof pitch is lower on the windy side which leaves a 16 inch gap at the gable, you get a good draw with just a little wind, the 10 foot pens will hold 2 head if needed and let the gates swing to hem a silly one behind the gate rather than having to go to a chute. First pen one each side is wash rack and feed room. We put a second floor to the west a 10 x 30. It will cause the afternoon sun to get blocked and cool down starts by 3. Up stairs makes a bunk house for us.
Ours is 6 years old, pipe frame, tin roof and walls, finishing the up stairs was costliest, plumbing and elec, plywood floor. You can make it from about 6, all the outer fences are electric, one pen is paneled, use it until calves learn the electric. Its 100 plus starting in may here, I'm not big on fans, the arctic misters are enough to keep it cool on most days.