How does the act of writing a Guru's biography contribute to the community, according to the preface?

The preface explains that writing a detailed biography is a profound form of Guru service. Chapter 0 states that the Sadguru accepts service from devotees by having his biographies written. When a writer creates a comprehensive work like the Shri Sai Satcharita, they are performing a direct service to the Guru. Furthermore, this act extends to the wider community, as when other devotees study and perform Parayans of the book, the writer gains the merit of 'serving God in humanity (Jan-Janardan) and public service,' thereby helping others achieve their life's purpose and solidifying the community's foundation.