Can you explain why Maharaj, who initially took little from Kashiram, later started demanding so much Dakshina that Kashiram went into debt?

Maharaj's actions were a deliberate spiritual 'Leela' intended to help Kashiram overcome a specific spiritual obstacle. According to Chapter 0, Kashiram developed pride from being a donor, feeling bad if Maharaj didn't accept his Dakshina. This pride, the feeling that "I have the power to give," is an obstacle to spiritual progress. To remove this pride, Maharaj first allowed Kashiram to face financial difficulties and then began a "barrage of demanding Dakshina," forcing him to borrow. Once Kashiram was humbled and realized he truly lacked the power to give, his pride vanished and his prosperity was restored.