Currently, I am trying to make indoor levels using my blender modeling software (as I am on a budget of $0), and would like some advice on what to do with this problem. I want to make it easy to texture but easy to work with in unity also. Any help is welcome.
You need to model the indoor elements in Blender. UV unwrap it there as well and see how the textures look. Once that is done, import it to Unity. Now you probably want to place colliders. If you have a flat ground, use one or more box colliders. The same for the walls.