When to tranfer my domain name from Wix to WordPress ?

Hi, first of all thanks to all of you who helped me a lot with this forum, you’re doing a great job !!
My question is :
I have an old weebsite I don’t want anymore with WIX. I don’t care about the content because I want to make a brand new one with WORDPRESS, but I would like to keep my old domain name. So, what would be the correct way to do this ? :
I want to keep the old website online meanwhile I prepare the new one with wordpress but do I need another domain name to start working on it ? Will I have to transfer the domain name to the new hosting before starting the new website ?(but if I do so, the visitors won’t be able to access to the old one during my creation process …)

I thought I could access to my wordpress hosting and start working without having any domain name at the beginning and when finished, transfer the old domain name to my new website, that’s the idea.

I hope you will understand my questions, I am a little bit confused with this process.
Thank you.

Dani.