The National Coalition for the Homeless has fact sheets you can download to learn about Homelessness in the US. There is also information on how you can help.
"In 2003, children under the age of 18 accounted for 39% of the homeless population; 42% of these children were under the age of five (National Law Center on Homelessness and Poverty, 2004). This same study found that unaccompanied minors comprised 5% of the urban homeless population. However, in other cities and especially in rural areas, the numbers of children experiencing homelessness are much higher. According to the National Law Center on Homelessness and Poverty, in 2004, 25% of homeless were ages 25 to 34; the same study found percentages of homeless persons aged 55 to 64 at 6%." (National Coalition for the Homeless)