For one Bangor family trying to make ends meet, a lost purse holding the rent money was all it took to tumble to the edge of homelessness. Today, mother and son cling to a hotel room, working with local agencies to try to avoid a stay in a local homeless shelter and the trauma that can come with such an experience.

This is not an isolated story. In Maine, a family is considered extremely low income if the total household income is $16,767 a year or less. An elderly or disabled person who relies solely on federal Supplemental Security Income has an annual income of just $7,236. However, in order to afford even a modest two-bedroom rental home in Maine, the household income has to be at least $29,208 a year. Maine has a shortage of roughly 16,000 rental homes that are affordable and available to extremely low-income families.

This shortage is replicated across the country. Nationwide, there are 9 million extremely low-income renter households and only 6.2 million homes renting at prices they can afford, paying the standard of 30 percent of their income for housing. This is a shortage of more than 2.8 million homes. While higher income families may have trouble affording homes they prefer, extremely low-income households are the only income group for whom there is an absolute shortage of homes.

The consequence is that the lowest income families must spend more than they can afford for housing. In fact, 71 percent of all extremely low-income renter households in the United States – and 55 percent in Maine – pay more than half of their income for their homes. Spending most of household income for housing means there is not enough left for other basic necessities, forcing families to choose between paying the rent, paying for heat or buying food or medicine. Certainly, they are not able to save for the future. The ultimate consequence of the housing shortage is, of course, homelessness.

Once a family has lost its housing, additional traumas often arise. Parents may have to give up a job if the shelter they find is in a remote place. Children may have to change schools and doctors. Health care is always a concern for those who are homeless, whether they are living in a shelter, moving from place to place, or sleeping in abandoned buildings or in a car. These concerns mean that housing instability affects not only the families in question, but also outcomes for school systems, health care providers and state housing policies.

This is not a problem that can be solved by the private housing market alone. If a profit could be made in building and operating housing that extremely low-income families could afford, the market would have long ago responded to this acute need. As with other market failures in the provision of basic needs, public investment is required.

In response to the affordable housing crisis, more than 5,600 national, state and local organizations, religious leaders and state and local elected officials have endorsed the establishment of a National Housing Trust Fund. The goal of the national housing trust fund is to support the production and preservation of 1.5 million homes for extremely low-income families over a 10-year period. National Housing Trust Fund legislation, co-sponsored by concerned members of Congress on both sides of the aisle, is expected to gain approval by the House of Representatives later this month but faces an uncertain fate in the Senate.

Safe, decent, affordable housing strengthens families and builds communities. Ensuring housing security for the poorest among us is an investment we simply cannot afford to pass up. We urge Sens. Olympia Snowe and Susan Collins to join Reps. Tom Allen and Michael Michaud in supporting the National Housing Trust Fund legislation.

Nicole Witherbee is a federal budget analyst for the Maine Center for Economic Policy. John Anton is chair of the Maine Affordable Rental Housing Coalition.