Does Sonic Fusion FTTN come with a domain registration (transfer)? Or, is that an additional cost?
All connectivity services come with free personal hosting (register a new domain name for free - it's hosted for free as long as you continue to have connectivity services, but there is the annual registration renewal of $15 after the first year).
If you want to host a domain that's already registered with us, you'd need to purchase a hosting service depending on your needs: https://www.sonic.com/business/hosting