Doing it in a way that works when the relationship ends.
THE OPTIONS
The client holds their own account, and you are added as a contact. Cleanest. You hold the account and bill them. Simple, but you carry the risk and they have no direct relationship with the host. Reseller hosting. Designed for this, and gives you margin and control.
WHICHEVER YOU CHOOSE
Put it in writing: who owns the account, who pays, what happens at the end.
DOMAINS
Register in the client's name as registrant, with yourself as technical contact if you want notifications.
Never register a client's domain in your own name. It creates a dispute when the relationship ends, and in most cases the client is entitled to it.
WHAT TO SET UP
Account and mailboxes SSL and forced HTTPS The cron job, since HTTP wp-cron is blocked Backups, configured and confirmed running A cPanel contact address not on the hosted domain
WHAT TO DOCUMENT
Everything, somewhere the client can reach it.