Do I have to pay fee for using Unreal in Production Company


The question concerns using UE4 in production company.
We deliver glass products as glass doors.
What we want is to create product configurator in UE4 that will let users to “customize” their own glass doors.
The product configurator would be used by our partners in local business points so when client will come to the business point, our partner would show the client the “possibilites” in glass door customization.

Please explain, how it would be calculated how we are obliged to epic games?

Thank you,

Best Regards