As others have said, build as big as you can. 24x48 is quite small for what you describe. Why spend money on something and it's too small the moment you move in?
Perhaps to stretch the budget you can build the shell right now (big). Next year install the power and water. Following year the concrete. Following year the bathroom fixtures and so on.
That was my strategy more or less. Mine is 40x72 and I need to build on or build another one. Thinking maybe a 30x50 just for tractor and implement storage. Wife is not so encouraging so I will be waiting a few years.
Another point. Deeper is nice for hitching your trailer to your truck and being able to keep it inside. Very handy. Also, consider what you may own during the time you have this building. Make it big enough to fit. In our case, we have outgrown our big enough building within 5 years. Now we are talking about room for the boys' car(s) when they begin to drive (in 9 years - ha!) and also if we get a boat, cab tractor, or...? Also be nice to have one bay dedicated to a lift. That's more space occupied.
I am firmly of the philosophy that everything mechanical should be inside. My equipment does not suffer from weather related deterioration, which saves me money and makes life easier. You live in an area of the country where frost and snow are more of a concern. I would think it is preferable to have everything inside up there.