Raising a child is not cheap. Now try raising one on a fixed income and long past the age one associates with parenthood: 65 years and older.

More than 300,000 grandparents in California have primary responsibility for their grandchildren, and of this group, almost 65,000 are over the age of 65. More than 20,000 care for their grandkids without any extended family assistance at home.

A new study from the UCLA Center for Health Policy Research and the Insight Center for Community Economic Development shows that these families - older adults raising grandchildren alone - may be among the most vulnerable residents in California, due to the state's high cost of living and low levels of public assistance.

"California's high cost of living turns the loving act of caring for a grandchild into a desperate financial risk," said the UCLA center's D. Imelda Padilla-Frausto, lead author of the study. "And older grandparents, many on fixed incomes and with limited mobility, are often the least able to advocate for, and access, public assistance."

The brief's new calculations - based on the true cost of living in every California county - show that nearly half of custodial grandparents who are 65 and over in California do not have enough income to cover the most basic needs of the grandchildren placed in their care. Yet public programs that might provide benefits that could help grandparents cope, such as the state foster-care program, are often difficult to access or off-limits altogether for family caregivers.

"There is a hypocrisy built into how assistance is allocated to children and their caregivers in California," said Susan E. Smith, director of the California Elder Economic Security Initiative at the Insight Center. "We preach the importance of keeping families together yet deny grandparents essential assistance because they are 'family.' This is an injustice that policymakers could easily address by making more benefits available, and accessible, to grandparents."

Many older adults in California are ineligible for public programs like Medi-Cal, housing subsidies and food benefits because they have incomes that are above, often just slightly, the federal poverty level (FPL), which is the official federal definition of poverty. Yet this definition - $18,530 for a family of three and $14,710 for a family of two in 2011 - is considered by many experts to be inadequate, largely because it does not take into account variations in the cost of living from state to state and county to county.

Grandparents whose incomes leave them above the FPL but below the income needed to cover their basic needs may struggle in a high-cost county such as Los Angeles or San Francisco. The costs involved in caring for a grandchild (or two) far exceed the FPL in every California county. For example, in 2011, an older couple with one grandchild who lived in a two-bedroom rental needed an income as high as $49,942 if they lived in Santa Cruz County and as low as $32,965 if they lived in Kern, the "lowest-cost" county.

Among the study's recommendations, the authors suggest raising the eligibility criteria for certain public programs to 200 percent of the FPL; extending state foster-care benefits to kinship caregivers; and limiting the frequency of cumbersome and bureaucratic benefit renewals (since most older adults live on fixed incomes and thus do not experience income fluctuations that require regular documenting).

The data on the costs of raising a grandchild are part of a larger release of 2011 Elder Index data on the true cost of living for older Californians.

Updated every two years by the UCLA Center for Health Policy Research, in partnership with the Insight Center for Community Economic Development, the Elder Index quantifies the cost of basic necessities like food, clothing and shelter for each county of California and is part of a national movement to improve the way poverty is measured in the U.S. The methodology for the basic amounts was developed by the Gerontology Center at the University of Massachusetts - Boston and Wider Opportunities for Women in Washington, D.C.