Mud will depend on your ground mostly. I have very sandy soil and had sand brought in to build up a pad for the barn. As long as I keep up with the manure and wasted hay I have very little mud. Even with a year like we've had where its day after day of rain. If you have a soil that doesn't drain well you'll have to grade in some swales most likely or do some sort of drain (tiling, french drain etc.) to deal with water.