An individual AdWords account can be linked to no more than five Manager accounts. You can refer to the account limits documentation listed
here. This said,
BudgetOrderService enables only the approved managers to create account-level budgets for the client account. The invoicing and payments are not affected when an account is linked to a new manager account. However, the newly linked manager account will continue to have access to the account's billing and sign-in information. Even if the AdWords account is linked to multiple Manager accounts, only one budget will be active at a time. It is not possible for MCC-B to make any changes to the existing BudgetOrder of your account, but they can create a new BudgetOrder when the existing budget is completed.
Let me know if you have any other questions.