Does Coinbase have a $0 balance?

Could you please clarify for me if Coinbase maintains a zero-dollar balance? I'm curious to know if users are able to have their accounts with no funds at all, or if there's a minimum balance requirement. It would be helpful to understand if this platform allows for complete flexibility in terms of maintaining a balance, or if there are certain conditions or policies that govern this aspect. Thank you for your assistance in clarifying this matter.