I just started using Unity 3D only a couple days ago and I’m not too sure how to work some things. I’m starting to make a cool game, but it would help out a lot if i knew how to make a cube or any other object hollow. If there’s no way to do this by just using Unity 3D, please list some programs that are good for doing things related to this. Thanks 
Blender, Max, Maya, many others.
But if you really just need a hollow cube, you can construct one from 6 planes. Just group them under an empty object and rotate and move them into hollow-cube configuration.