Steps for transferring ownership of third-party theme (Archetype themes)

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Hello Friends,
I'm planning to use the Archetype theme's Motion -theme for the next project for my client. How I should proceed with the theme and its purchase?
Do I start:
1. Development store on my Shopify Partner account >>
2. Go to Shopify theme store and purchase the Motion -theme >>
3. Build my client's store and when it is ready >>
4. I transfer the ownership of the store (similar way as I do when I build the store using Shopify's own theme)
Or is this the right way to transfer ownership to the client?
What things do I need to consider when buying a theme from the Shopify theme -store, but which Isn't Shopify's theme?