Creating levels from tile set

I am a little confused as to how I want to do this. I am using Unity free. Is there any native support for tile set level design? I am not looking to buy anything mods from the asset store (mostly what google has told me).

Bacially, have a script with these:

-A gameobject that stores what tile is currently selected

-A array that holds all the tiles that can be selected

-A OnGUI function that has multiple buttons, each changing the main gameobject
to whatever tile you want to the button to that’s int he array.

Thank you!