Young man in car waving goodbye to parents © OJO Images, Getty Images (Young man in car waving goodbye to parents © OJO Images, Getty Images)

More than one-third of millennials, aged 18 to 31, still lived with their parents in 2012 -- the highest percentage in at least four decades. There are several factors behind the trend, including higher unemployment, delayed marriage and rising college enrollment.

There also seems to be a growing acceptance that it's OK for twenty-somethings to hang out at home for years longer than past generations did. For those who are ready to leave the nest for good -- and their parents -- some common-sense tips might help make the journey safer and easier.

Dear Liz:

I'm 28 and sharing an apartment with my mother and three of my siblings. I can't really afford to live on my own. Debt is up to my eyeballs. What can I do?

-- Tarah

Dear Tarah:

It may comfort you to know that you have plenty of company. A Pew Research Center analysis of U.S. Census Bureau data found that 40% of young men 18-31 and 32% of young women lived in their parents' home as of 2012. Part of that may be explained by rising college enrollment: In March 2012, 39% of those aged 18 to 24 were college students, compared with 35% in March 2007.

But even among the unemployed, the single and those in college, a greater share lived with their parents in 2012 than in 2007, suggesting a growing acceptance of the phenomenon.

Image: Liz Weston

Liz Weston

Most people aged 18 to 34, and most parents, believe it's acceptable for college graduates to live with their parents for up to five years after they finish school, according to a Coldwell Banker Real Estate survey. (Those age 55 and older generally believed that even three years was too long.) Meanwhile, one in four parents believe it's OK for adult kids to live with their parents as long as the kids want.

Returning to the nest may be a comfort for both kids and parents, but there are plenty of potential problems. Emotional and financial development is delayed, since establishing independence is an important step in adulthood. Meanwhile, leaning on your parents financially can hurt their ability to save for retirement, which means someday they could boomerang on you.

So it's time to make a plan:

1. Review your employment prospects. Are you trying to get by on a below-average salary in a place with above-average living costs? Millions try to scrape by in notoriously high-cost cities such as New York, San Francisco and Los Angeles, often with disastrous financial results. Moving somewhere cheaper could help you jump-start your transition to adulthood. You don't have to live in the boondocks or even accept permanent exile from your hometown. You just have to find an area with a cost of living that makes sense, giving your current means.

2. Consider adding a side job. You have more energy and fewer obligations than you likely will in a few years, so now is the time to really hustle to earn that extra cash. Read "Should you take a second job?" for more.

3. Aim for a rent that is no more than 25% of your income. In many areas, that means you'll have to find roommates. Spending much more on housing could leave you without enough cash to pay your other bills, reduce your debt and save for the future. Other options to get cheaper rent: Manage an apartment building, live as a companion to an older person or offer yourself as a live-in, part-time au pair to a family with kids.

4. Come up with a strategy to deal with your debt. If you have federal student loans, it's often advantageous to consolidate them into one loan with the longest payback period possible. This will free up cash to throw at other, more troublesome debts, such as credit card bills and private student loans. Once those obligations are paid off, you can return to your federal loans and make extra payments to retire the debt faster. For more, read "A debt payoff plan that works."

5. Adjust your expectations. Unless your family is fairly poor, you're unlikely to be able to match the lifestyle they provided when you move out on your own. That could mean doing without stuff you take for granted, such as pay television, a fat data plan for your phone, new clothes and eating out frequently. The good news: If you make smart financial choices now, you should be able to restore these luxuries in time. The better news: Meeting the challenges of adulthood on your own will demonstrate what you can accomplish once you put your mind to it. That knowledge will help you surmount obstacles and succeed for the rest of your life.

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.

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