Who pays for what: a shared-house expense map
Make a one-page list: rent, utilities, internet, household supplies, parking, subscriptions, groceries, repairs, and furniture. For each item, name who receives the bill, who pays first, the due date, and how it is divided.
Include irregular costs such as move-in supplies, holiday guests, or annual fees. Decide whether they need prior approval. Keep personal purchases out of the shared map unless everyone agreed they are shared.
Review the map after the first month. It is easier to fix an omission before it becomes a grievance.