My business partner wants owner access as well. Can there be two owners?

Not today. There is one owner account, the one that signed up, and it can never be removed. Everyone else you add under Settings → Team is a manager, up to five of them, each with their own email and a one-time password you hand over. A manager runs everything day to day and is refused only three things by name: the WhatsApp connection and its groups, cancelling an order already delivered, and Plan & billing. If your partner needs those, the owner does them. Please do not share the owner login, because the change log is only worth something when it names who did what.