At the start of the rental
Finding a tenant, meeting the tenant + checking their reliability and solvency, drafting the rental agreement, signing the lease on your behalf, securing the rental deposit before handing over the keys, organizing and assisting with the initial inspection, meter readings: electricity, gas, heat meters, hot and cold water, meter transfer, checking tenant insurance before handing over the keys and on every anniversary of the lease, providing tenant details to the building manager, ordering nameplates for the tenant (doorbell and mailbox), collecting legal documents (EPC: Energy Performance Certificate, electrical certificate, etc.), and handing over the keys to the tenants.