Walnut Creek, Calif. ? When Jim Maddox got the news that he was going to be a grandfather, he was bewildered. Maddox, then 43, sat down for hours and contemplated what the new family addition meant to his life.

“I’m going to be a grandpa,” Maddox, a Concord, Calif., paramedic, recalls thinking. “I have a demanding job. My wife and I are in the middle of our lives.”

Then, little Cory came into their lives. And the overwhelming love he feels for the boy, now 9, is something Maddox says he wouldn’t give up for the world. In fact, for Maddox, who is now 53, and his wife, Rhonda, 51, being content as a young grandparent came easy. They were young when they had their own daughters. And some of Jim’s favorite childhood moments, such as climbing the Oregon mountains in search of berries, were with his own fortysomething grandfather.

“We wanted to be younger grandparents, so we can be active in the children’s’ lives,” says Jim, who is also grandpa to Abby, 5; Gavin, 4; and Emma, 2. “I’m still working and making money, so it gives us the ability to do all sorts of things. And, we still do the roller coasters with them.”

The Maddoxes and other grandparents around or younger than 50 hear it all the time: “You’re a grandparent? But you’re so young!” That’s a perk. But being a modern-day young grandparent is also a lifestyle feat. They have dynamic lives, often juggling careers and relationships with a very active role in the care and rearing of their grandchildren. Remember the other saying about the ease of being a grandparent? All the joy and none of the responsibility? It doesn’t apply as much as it once did.

Despite the recession, it’s an excellent time to be a grandparent, particularly if you’re part of the enormous baby boomer generation. These boomers make up the majority of first-time grandparents. They are at their youngest in decades. Parents first become grandparents at the median age of 50 for women and 54 for men. In 1985, the majority of grandparents were 65 and older, according to Susie Owens of Grandparents.com.

In fact, by the end of the year, baby boomers ages 45 to 64 are expected to make up the majority of the grandparent population. Their income is the highest of any age group. And because more than half of grandparent-homeowners do not carry a mortgage and continue to work past traditional retirement age, they were in a position to spend $52 billion on their grandchildren in 2009, according to The Grandparent Economy, a study commissioned by Grandparents.com. You may remember having young and relatively active grandparents, but their portfolios didn’t impress in this way.

“These grandparents are shifting the attitude of what it means to be over 50,” Owens says. “They’re more likely to be playing Nintendo Wii with their grandchildren than sitting in the corner knitting. They may be retired but they’ve taken on a new business. They travel. Or maybe they’re taking care of their grandchildren full-time.”

Rhonda Maddox retired from her job with a national cheerleading company to be a full-time baby-sitting grandma, but she still runs community youth cheer teams, and her granddaughter, Abby, is one of her pupils. You’d think a cheerleading fiftysomething wouldn’t want to be called the “G” word during practice, but Rhonda loves it. “I wanted my grandkids to call me grandma because it was such an honor to be theirs,” she says.

Giselle Vieto of Fremont, Calif., had a hard time with the moniker. Vieto, who is 48 with three grandchildren 7 and younger, has the kids call her mamagita, a term of endearment in her native Costa Rican Spanish. Two years ago, she and her husband George knocked down a wall in their five bedroom home to make room for their daughter Janice, son-in-law, Andrew, and the couple’s son, Freddy, who is 2. The Vietos’ twentysomething sons, Joey and Gino, also live with them.

“The economy is so difficult right now that if they want to save for their future, this was the best way to go,” says Giselle, who works full-time as the program director for Fremont Healthy Start. “As soon as I get off work, I pick little Freddy up and take care of him until mommy and daddy get home.”

In some ways, it’s like being a mom again. Particularly with Freddy. That concept really hit her when she was at a recent barbecue with adults her own age. Giselle was the only one with a toddler in tow. Still, her original vision of life with grown children wasn’t that far off.

“We come from a country where kids stay with parents until they’re older, so it’s not (unusual),” Giselle says. “My husband and I like to take motorcycle rides together during the summers, but it might conflict with the commotion at (her home) Grand Central Station.” But she would never trade the commotion and joy that comes with a full house. “When your youngest child is 20, you forget what kind of faces little kids make for certain foods. Those nostalgic memories are awakened.”