Is there a way to validate custom templates for copyrights?

Looking for a way that I could have my own custom templates validated in order to show my customer the autenticity of my work. My main concern is not much about copyrights because that's something that will pertain to my customer after he purchase my design time, (I have no worries cause they are being made as of now by myself and my wife) so the templates are just fresh from me and I want to give my customer some goodwill that they are unique and sold once.

This service I'm going to be promoting is just like the templates in templates monster with a lower price and I'm going to be selling all of them 1 time each one.

I'm not looking to spend heavy money on this so if you have a really affordable service or better yet something free please let me know.