2. Same answer as question 1. Also, just to add to this, most students are pretty honest since we're likely to be friends at the end of the program anyways.
3. They normally pay through a share of their monthly income. If they are laid off, and therefore don't make any income that month, they don't pay us anything. However, the payment is then deferred until they can pay again, for a maximum of 2 years, after which everything left is absolved. The goal is to never have anyone have to pay money they don't have.
4. 7% of the total income received. They still pay through a share of their monthly income.