Onboarding has phases: Discovery (what do they have?), Documentation (write it down), Standardization (push the MSP (Managed Service Provider)'s baseline tools), Stabilization (fix the worst issues), Steady-state.
Standard rollout: RMM (Remote Monitoring and Management) agent, EDR (CrowdStrike/SentinelOne/Huntress), backup, MFA (Multi-Factor Authentication), baseline CA (Conditional Access), patch policy, asset inventory.
Bad onboarding poisons the contract. Take the time.