Custom domain name

I want to know if to set a custom domain name has a cost on Netlify.
I have a free account for now, but I’ll soon get the Pro version.
Is it necessary to have a pro version to set a custom domain name ?
What else should I know…

I thank you guys for your answers already !

@phil1 If you were to purchase a custom domain that would obviously have a cost, either through Netlify or any registrar, but there is no charge with Netlify to assign a domain to a site instance, you can do that with the Starter plan.

Thank you very much.
It completely answers my question