They are not the very young, tempted by the freedom of their first credit cards. They are not the elderly, trapped by failing bodies and declining savings accounts. And they are not a random assortment of Americans who lack the self-control to keep their spending in check. Rather, the people who consistently rank in the worst financial trouble are united by one surprising characteristic. They are parents with children at home.(p.6)

While this may in a way seem logical (i.e., people, especially single mothers, who have more financial obligations are at more risk), the question which immediately comes to mind is: Shouldn't this be impossible specifically in the two-income family? Isn't it exactly to prevent this from happening that they both have jobs?

Consider, however, the following: Way back when women were not expected to work, they would be at home, taking care of the kids, their elderly parents, and the sick. If a child became ill, a grandparent needed more care, or someone had an accident, they would be cared for without the family income taking a hit. And if dad was the one to become ill, mom could choose to enter the workforce – earning less, of course, than dad had been, but generally they would still be able to rake in about 60% of what her husband used to earn (p.59). Nowadays, of course, the normal situation is one where both parents are working, so that, as soon as either worker becomes ill or is laid off, the family income will on average be halved almost immediately. And this is a problem because the average family is spending nearly 50% of their income on the mortgage payments, leaving less money for discretionary spending now – with both parents working – than in the 70s with only one ‘working’ parent, and no backup worker for when something goes wrong.
The question here, of course, is why people are so (I would indeed call it that) foolish as to buy a house which required you to take out a mortgage that basically eats up an entire income. The answer to this question is two-fold, with one half being due to market forces, and the other to legislation.

As most readers will probably know, the US has a school system where you can only get into certain schools if you belong to the zip code area for that school. As such, if you are worried that the school in the area you are living in is bad, you will have to move to another zip code area. And in reality this meant moving out of the inner cities into the suburbs, which were perceived to be safer, as well as offering higher quality education. This, of course, means that housing in those areas will be relatively scarce compared to housing elsewhere, which in turn means higher prices. Now, once people started having a second income, this meant that more could be spent on the mortgage, and, when the lending market was deregulated early in the 1980s, there was no longer an imposed limit of 30% of total income which could be spent on mortgage payments. This meant house prices could rise a lot, with the bidders having to choose between the fear/thought of “not giving your children the chance they deserve” and trying to make ends meet (and all the risks that that entails):

By way of example, consider University City, the West Philadelphia neighborhood surrounding the University of Pennsylvania. In an effort to improve the area, the university committed funds for a new elementary school. The results? At the time of the announcement, the median home value in the area was less than $60,000. Five years later, "homes within the boundaries go for about $200,000, even if they need to be totally renovated." The neighborhood is otherwise pretty much the same: the same commute to work, the same distance from the freeways, the same old houses. And yet, in five years families are willing to pay more than triple the price for a home, just so they can send their kids to a better public elementary school. (24)

So, we’ve got enormously increased housing costs, a family with two people working who must bring in twice as many paychecks as before to live at the same level of comfort (with a more-than-doubled chance that something will go wrong: "A family today with both husband and wife in the workforce is approximately two and a half times more likely to face a job loss than a single-income family of a generation ago." (82-3)). And then there is the socially pretty much invisible disease of bankruptcy, apparently quickly becoming just as prevalent as divorce (and sometimes accompanying it). The point with bankruptcy, of course, is that people try like the plague to avoid it. Once someone is laid off, most families seem hold out the hope that they will quickly be able to find a new job, and generally use their credit card to make up for the temporary difference in income, figuring they will be able to pay it back when they've got 2 jobs again, rather than deciding their only recourse is to take their child out of the school he/she is in, and move to another district, where housing is cheaper (and schools are potentially worse). This is, of course, statistically quite unrealistic, because even when they are able to find a job in, say, 3 months, they will be unable to save enough money every month to pay back the loan with. And so, after a while, they start incurring quickly-mounting "late fees", enormous interest hikes, and, oddly enough, more offers from credit companies to take out yet more loans, second or third mortgage, and so on, with the end result generally being (de facto) bankruptcy even when people do not file for it. ("In 1981, the median family filing for bankruptcy owed 80 percent of total annual income in credit card and other non-mortgage debts; by 2001, that figure had nearly doubled to 150 percent of annual income." (77)) Consider what they have to contend with:

After he suffered a heart attack, missed several months' work, and fell behind on his mortgage, Jamal Dupree (from chapter 4) got the hard sell from his mortgage lender. When Jamal missed a payment, the mortgage company sent him dozens of personalized letters with a single goal—to persuade him to take out yet another mortgage. "They'd send out a notice, saying 'you need a vacation, take out this thousand dollars and pay it back in ninety days.' If you didn't pay it back in ninety days, they charged you 22 percent interest." When he didn't respond to the mailers, the mortgage company started calling Jamal at home, as often as four times a week. Again, the company wasn't calling to collect the payments he had already missed; it was calling to sign him up for even more debt. Jamal resisted, but his mortgage lender didn't let up. "When I turned them down, they called my wife [at work], trying to get her to talk me into it."(139-40)