NEW YORK (MainStreet) — Financially motivated matrimony is not a new idea. Perhaps our most famous cinematic depiction of the strategy comes from back in 1953's “How to Marry A Millionaire,” starring Marilyn Monroe, Betty Grable and Lauren Bacall in a post-war rom-com romp.

But funding a retirement by marrying rich receives surprisingly scant attention from financial planners. And opportunities to secure a financially comfortable at the altar do exist. Some 12% of federal tax returns with million-dollar annual incomes list the taxpayer as single, according to the Tax Foundation. In 2010, the latest year for which the organization analyzed IRS data, that came to 32,000 potential human 401(k)s.

Perhaps unfortunately, the single million-dollar earners also tended to be older. About 80% of millionaires were older than 45 and close to half had passed 55, the Tax Foundation reported. There was no data on the gender distribution among millionaire filers.

The good news is, those unmarried high earners may not be out of reach for suitors who come from humble circumstances. Married couples today often have contrasting socioeconomic backgrounds, according to Jessi Streib, an assistant professor of sociology at Duke University and author of The Power of the Past: Understanding Cross-Class Marriages (Oxford University Press, 2015). “Those are becoming increasingly common and they’re not that unlikely anymore, assuming the people end up in same social class as adults,” Streib says.

Although growing up poor may not be an obstacle to marrying rich, Streib cautions that the situation is different for people who inhabit opposite ends of the affluence spectrum as adults. “Marriages between somebody who is currently wealthy and somebody who is currently poor are very unlikely,” she says. “The chances they’ll meet in the first place are small. And the chances the wealthy person will be interested in the poor person as a romantic partner are also small.”

This is not to say that gold-plated knights don’t occasionally rescue impoverished princesses, and vice versa with gender roles reversed. Russell Luna, a Denver financial advisor who in his work as a Certified Divorce Financial Analyst, consults with couples dividing up the financial fruits of foundered partnerships, sees a fair number of partners who bring very different resources to a union. “There are a certain percentage of people that do look for someone to take care of them,” Luna says.

Some wealthy spouses employ prenuptial agreements to keep impecunious spouses from getting access to financial assets in the event of divorce. Prenups can be effective, Luna says, but he doesn’t see them often. Usually, judges, attorneys, mediators and the divorcing couple work out a negotiated division, not necessarily a 50-50 split, that is based one each party’s future earning power as well as needs for children and other expenses.

In the absence of a prenup, even an unsuccessful marriage can effectively fund a 401(k), Luna says, citing one case he’s familiar with in which a woman from a modest background married a college classmate whose parents were well-heeled enough to give him an oil company as a graduation gift. When the marriage broke up, she received about $500,000 in assets plus $150,000 a year in alimony for life. “So she’s still living comfortably,” he said.

Of course, staying married to a wealthy spouse is also a viable option. Another of Luna’s acquaintances married a woman from a wealthy family and today works only as a hobby, acquiring and running and selling small businesses to keep himself busy. His retirement, Luna says, “absolutely” is taken care of thanks to his wife’s trust fund.

If you’d like to snare such a spouse to support your own retirement, it takes planning. Streib says people with low- income backgrounds need to be moving in the same circles as wealthy people. That can be costly in itself, as to be accepted they need to have the right clothes and haircuts and also dine and vacation in the right places.

Ideally, wealth-seekers should also have similar educational backgrounds as their well-off targets, Streib adds. She says people of both genders today increasingly seek spouses with education and income similar to their own. “Even when men are marrying very attractive women, they’re often women from their class,” she says. “That’s partly because beauty standards are based on class as well.”

Marrying a millionaire today, it turns out, takes a set of attributes very different from those Mlles. Monroe, Grable and Bacall relied on. If you’re not already one of the financially secure class, matrimony may not be the best way to join it. “It’s probably easier to acquire your own wealth than to marry wealthy,” Streib says.