How to disable option for users who aren't logged in
Use the premium content module

Restricts access to premium content by role and provides a general API
for other modules to help decide if a user has access to premium
content.
This is useful on a news or membership site where teasers are
available to the general public but the full body is only available to
privileged users. Premium nodes appear in listings with full title and
teaser available to anyone. If a user does not have adequate
privileges, the default behavior is to show a simple message, but you
can use Panels or theme overrides to do more custom things.

All you need to do is enable the module, go to the edit page(admin/structure/types/manage/yourcontenttype) of the content type you want to make premium, and on the publishing options tab, select premium content