I got a shipping container when critters chewed my tractor's diesel return line while it was sitting in a pole barn.
It's very wet here 4-5 months of the year, and hot in the summers. Get the container off the ground so that there's air circulation below and you won't have condensation issues (and make it high enough off the ground at least at one end so that fox or bobcat can patrol underneath and keep critters from living under it!).
My container is placed on a slight slope (also helps with water probably) so it the main entrance end where my tractor goes in is up on a railroad tie (with a gravel ramp going in) and the other end is on two railroad ties to be level. (Mine is a 40' with doors at both ends - makes getting stuff from the middle or other end much easier.) Containers only need to be supported at the corners.
My container is light tan and the temperature inside is typically about ten degrees (°F) higher inside during the sun than outside - not too bad.