Domain Mapping Workflow and Details


I wanted to know few details about Domain Mapping.

1. After enabling this feature, how will my users add domain? I mean the workflow for a user to add a domain. Do I need to do anything everytime for mapping a domain to a user?

2. For example, If I keep my pricing plans including the domain name will that work? Or the user should manually buy domain name after singing up to the pro plan?

3. Along with domain name, is there a way to provide Email account to the user for his mapped domain?

Kindly help me out with these doubts.