How to copy content type? How to copy content type in Drupal 7 ? 

I can't find a button to duplicate content type.
Maybe too late you can use the Bundle Copy module:


  Bundle copy is a replacement for the Content copy module which lives in the CCK project for Drupal 6.  Has export/import support for: Node types, Taxonomy, User, Field API fields, Field groups


UPDATE 7.x-2.x-dev notes

The following features have been added:


Export/import of Field Collection
Cloning of Content types
Export/Import of Commerce Entity bundles


Drupal 8: Bundle Copy is in Drupal 8 Core CMI.