In February, retirees Ken and Sue Drenth will embark on their eighth volunteer stint since 2006.

They will be returning to Arkansas's Heifer Ranch, an educational center for the nonprofit Heifer International, which provides livestock and agricultural aid to people suffering from starvation and malnutrition.

"I had grown up on a farm and my wife had grown up in an urban area... so we said, 'What the heck. Let's try it for a while," said Ken Drenth, 67. "We loved it."

The couple will spend nine weeks as live-in volunteers working on the ranch. In the past, Ken has done everything from building fences to birthing calfs, while Sue has helped with the development of conferences hosted at Heifer. In exchange, they receive free housing and a small stipend.

The couple receives pension benefits from their years of working in the public school system. So the financial benefits are an added bonus for their stay. But they said that retirees of all means would be able to live comfortably there.

"The culture of the ranch is one of great frugality," Sue said.