Each account (IG page for example) will be a separate Manychat account. The billing for each account can be different (so each of your customers can pay their own Manychat).

You will have a personal Manychat account associated to your FB personal profile. With this profile, you'll have access to many Manychat accounts (associated to pages/businesses).  I have access to probably 200+ MC accounts with my personal profile.

Your clients will have access only to their pages.

So Business A will have you and Manager A as the account admins, and will be paid with their credit card.

Business B will have you and Manager B as the account admins, and will be paid with their credit card.

And you'll have your Agency's account, paid by you and with you and your team as Admins.

Does this make sense?

Ok, so each of my clients has to create a manychat account and pay themselves, then add me to their team members so I can be the chatbot on their profile? Does this not raise intellectual property issues? Because if they have permanent access to my chatbot, they can keep a copy of it? 

I have the same question,

I want to manage my clients chatbots without being their actual page’s admin, because its not secure to have all their passports and personal details, also they should not have access to the manychat account that I manage, otherwise they can copy or change the bots.