Settle ownership before you build. Decide who will hold the account, who pays the plan and who owns the domain, because changing those after launch is where most handoffs go wrong.
If you are still choosing a builder for client work, read the client sites comparison first, then the editor seat costs guide to see what it costs when the client or a collaborator needs to edit. Those two answers usually settle which builder to quote.
When the site is ready, follow the transfer guide for your builder step by step and use the handoff checklist to confirm the client can log in, edit, renew and recover access without you.