"The simple fact is that most people are not in a position to accumulate enough assets. … They need to be able to pursue other forms of income to supplement that lifestyle so that money can last as long as they do."
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As many as 9 million people aged 44 to 70 are getting paid for work that combines their personal passion with a social purpose, according to the nonprofit group Encore.org. An additional 31 million are interested in making the leap into "encore careers."
They're seeking new careers in the nonprofit world: health care, education and government. While doing altruistic work can mean a cut in pay, having some income can help those who aren't ready to retire just yet.
Louisa Hellegers, 65, said self-reflection was essential in helping her figure out what to do next. After spending more than four decades in publishing, the senior executive said she started "thinking about who I am, where I've come from, what I wanted to do."
Hellegers said she decided "what I wanted to do is what I have been doing my whole career … serve and give back in various ways to the community."
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She's now using her skills as a human resources executive, focusing on people, not publishing. Hellegers is the director of organizational development at the Center for Employment Opportunities, a nonprofit organization that helps men and women who are just getting out of jail find jobs.
Beth Kempner, a 54-year-old former advertising executive, is the director of public affairs at the organization. Like Hellegers, she found her position through a fellowship program run by Encore, which places highly skilled, experienced professionals at the end of their "midlife" careers into paid positions at social service organizations for their "second acts."
Kempner said while her agency's work is making a social impact, she finds her "second act" is personally fulfilling. It also provides some financial security. After the Encore fellowship, she was hired on staff at the agency.
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"You feel a little more fulfilled, I think, when you get paid for the work you do," she said. "This is not the same [money] as I was making in the corporate world, but you do feel good."
—By CNBC's Sharon Epperson. Follow her on Twitter