Darryl and Kristina Pendergrass and their sons, William, 3, and Ian, 20 months. The family gets by on Daryl's $43,000-a-year salary as a biologist with the Alabama Department of Public Health. Debbie Elliott/NPR hide caption

itoggle caption Debbie Elliott/NPR

Originally from St. Louis, Mo., Jada Irwin moved to the Washington, D.C., metropolitan area for work. As a single woman, she likes where she lives, but if she were to have children, she says, she would move to South Carolina or somewhere similarly less expensive. Mito Habe-Evans/NPR hide caption

itoggle caption Mito Habe-Evans/NPR

Sue Spencer, 50, stands with her daughter Gaelyn Spencer, 17, in front of their home in Marlborough, N.H. Erik Jacobs for NPR hide caption

itoggle caption Erik Jacobs for NPR