Despite her limited income of less than $20,000 a year, volunteering has helped 73-year-old Barbara Traynor afford the retirement she dreamed of.

Since retiring in 2005, Traynor has given her time at nonprofits and national parks across the country, in exchange for free room and board.

When she's not volunteering, she lives with her oldest son in upstate New York. And while en route to her volunteer stints, she's often able to stay with friends that she's met through her travels, making gas her biggest expense. She even wrote a book about her lifestyle, dubbing it "the pennywise approach" to retirement.

"I always wanted to see the rest of the country," she said. "There is so much to see out there."