Dotted with swimming pools and golf courses, the thriving seaside enclave of Ewa Beach perches just down the coast from bustling Honolulu, Hawaii. The island-style homes fronting palm-fringed streets offer views of two mountain ranges and proximity to some of the best big-wave surfing in the world.

This resort community, where houses sell from around $200,000 to more than $1 million, enjoys another perk: easy access to no-money-down home mortgages, guaranteed by the U.S. Department of Agriculture (USDA). The guarantees are provided to qualified buyers courtesy of the farm agency's rural housing program, created in 1949 to help lower-income Americans in rural areas who lacked access to "safe and sanitary dwellings" and couldn't get credit any other way.

Reuters found at least 250 of the loans in the Ewa Beach area. It also found them in a lot of other places that aren't very isolated or very rural: Los Angeles; Washington, D.C.; Austin, Texas; Seattle, Wash.; and Tampa, Fla. The mortgages pop up near Silicon Valley's Sand Hill Road, the main drag for high-tech venture capital, and a short distance from the headquarters of Google Inc., Facebook Inc. and Apple Inc, as well as in dozens of small to midsize cities across the United States.

All told, from 2003 to 2011, the USDA guaranteed at least 51,600 mortgages, totaling at least $6 billion, for people who lived in areas deemed urban by the 2000 U.S. Census, according to a Reuters analysis of Census Bureau data and mortgage lenders' regulatory filings. Read more.