The grandparent comment's specifics are off a bit, but I think the general principle --it takes money to make money -- concisely explains a good portion of the underclass' economic predicament.

I'm going to have a blog post about the economic situation that led me to taxi driving. The tl/dr is basically that they loaned me a car for 12 hours at a time. In the beginning I made enough to make it worth my while...