Bryan Caplan read Portfolios of the Poor: How the World's Poor Live on $2 A Day. The main lessons he took from it:

1. The income of the ultra-poor is not only low, but highly variable.  They rarely have regular jobs in a "sweatshop."  Instead, they desperately cobble together income from many different sources.  Many days they earn nothing at all.

2. No one, no matter how poor, lives "hand to mouth."  Even the poorest people save money, make investments, and plan ahead.

3. The poor also borrow a lot of money.  Who would lend to them?  For the most part, other poor people - family, savings clubs, small-time loan-sharks.  The rates are astronomical - 20% per month is pretty common.

4. Even the poorest people spend a lot of money on things other than food.  One of their main reasons for saving and borrowing is to pay for relatively lavish weddings and funerals.