Just how passive is passive income?

The opportunity to make money while we sleep is one few of us would turn down. And passive income, at face value, suggests we can do just that.

Social media is chock-full of influencers telling us how to make passive income. And while many of those content creators do actually earn money even when they’re not on the clock, fewer of them are forthcoming about the work required to get there.

"A lot of people are surprised by how much work it takes because I think a lot of people who are earning a passive income are talking about how great it is having earned that," says Pat Flynn, a California-based entrepreneur and creator of the "Smart Passive Income" podcast. "But they don’t necessarily tell you the whole truth. You’re seeing the tip of the iceberg."

"Passive" income, in most cases, won’t be created passively. Whatever the pursuit — investing in stocks to receive dividends, buying rental properties, earning ad revenue on video channels — you’ll have to put in work upfront before you can start making money while doing little, or no, work. And in many cases, you’ll have to keep doing work to maintain that income, too.

The taxes you'll pay on passive income may vary depending on the source of the money, so make sure you keep careful records of your earnings.

No set definition

When does a job or side hustle turn into passive income? That depends on how you define it.

There is no clear-cut point where income turns passive. For some, it could be when no work or upkeep is required, or for others, it could be when a minimal amount of work each week is required. And "minimal work" is also subjective.

"Passive income, for me, is really something that you have to work to set up, but after that, it takes very minimal work to maintain and to keep that income stream coming," says Joseph Hogue, a chartered financial analyst and creator of the YouTube channel "Let’s Talk Money."

Other sources of passive income include investing in bonds or peer-to-peer lending, generating ad revenue from a blog, or putting your money in a high-yield savings account. Even the money an artist makes through plays of their songs on a streaming platform can qualify as passive income.

Investing time or money

IFor most of us, creating this new revenue stream will involve investing money made from more traditional means like a job, or investing our time building a source of income from the ground up.

Without a large initial financial investment, people often underestimate the "sweat equity" or time and energy required at the beginning, says Jannese Torres-Rodriguez, a Florida-based entrepreneur and creator of the "Yo Quiero Dinero" podcast.

For both Torres-Rodriguez and Flynn, it took at least a year before they saw earnings from some of their current sources of passive income, such as blogs, affiliate marketing, ad revenue and selling courses, among others.

The amount of work upfront can depend on the income stream and what you want to get out of it. For instance, if you’re making income from rental properties, you can hire a person or a company to handle the property management. That’ll take away from your earnings, but putting in your own time will make the income more active than passive.

If you’re looking to make passive income, keep in mind there’s no promise your investment, whether that’s time or money, will pay off. Inevitably, there is risk involved.

Seeing other peoples’ successes, or hearing about them, can trigger that fear of missing out on a good thing. But before you try to emulate them, consider the journey. It’s not unattainable, but it won’t happen overnight.

Colin Beresford is a writer at NerdWallet. Email: cberesford@nerdwallet.com. Twitter: @Colin_beresford.