How much money does miss Caroline, the teacher, offer to loan Walter cunningham so he can buy lunch?

She offers Walter Cunningham a quarter.

This exchange provides an opportunity for Harper Lee to explain the economic situation in Maycomb. Walter Cunningham refuses the quarter since he cannot pay it back. From Scout's flashback, we learn how the Stock Market crash affected the economy in Maycomb. Farmers like the Cunningham's are barely making enough money to pay the mortgage. They are struggling just to put food on the table. We also learn that even though the Cunningham's may not be able to pay people with money for things, they will find a way to settle the debt by doing manual labor or delivering goods.