So a lot depends on what you plan to store in it. Tractors and tools don't require as much thought as does as say, canned food.
But you can look at either one of two ways when it comes to moisture- air exchanges or air tight. If you seal it up air tight you can rid the air of the moisture inside with Damp rid canisters or a dehumidifier. Otherwise, air exchanges- power vents up high with in-vents down low on opposite side. But you have to pull enough air so the inside temp is close to the outside or you will get condensation.
Depending on where you are, the temperature swings might not be that much, but here in NC we have days you run the heat at night and ac during the day, lol. There's not a lot to help with temperature unless you insulate and heat/ cool with outside source. They are just going to swing with the outside temp because they have no thermal mass to help stabilize temperatures