Faced with the harshest job market in nearly three decades, a growing number of out-of-work Americans are offering their services to companies for the promise of nothing but experience.

While these quasi adult internships are in dubious legal standing for employers, they offer unemployed men and women a chance to get their foot in the door and prove their value.

“They are not going to find a job sitting at home submitting resumes over the Internet,” said Julie Greenberg, co-founder of Jobnob.com, a Web site for job seekers and employees. “Job seekers are realizing that in this economy, they need to get out of their house and off of their computer. You’ve got to get creative.”

Charlie Hoehn knows firsthand just how tough the job market is. After graduating from Colorado State University with a degree in marketing in the spring of 2008, he received nothing but rejection letters for months until he changed his strategy.

“The market is so competitive. I was getting turned down because I was competing with 35-year-olds who were just laid off and willing to take a cut in pay,” said Hoehn.

Hoehn found some luck after offering his services pro bono to best-selling authors he really wanted to form a marketing partnership with.

He would tell them: “If you like what I’ve done, let’s talk about the potential to do more work in the future and receive compensation. If not, no hard feelings for me and no money lost for you.”

Hoehn, who recently wrote an e-book on working for free, parlayed these volunteer relationships into steady work. He helped Ramit Sethi come up with a marketing plan for his New York Times (NYT) best-selling book I Will Teach You to Be Rich and is currently traveling around the country promoting “I Hope They Serve Beer in Hell,” a movie based on a Tucker Max book.

Landing a Pro Bono Spot

So how do you find a volunteer position with a company?

Greenberg’s Jobnob.com, a Bay Area startup, has been holding networking events that connect job seekers willing to volunteer with cash-strapped startups. Greenberg said she was surprised by the turnout of interested volunteers, many of whom were in their 30s and had MBAs.

“We literally had lines out the door. We couldn’t accommodate everyone,” said Greenberg. Jobnob.com has already had five of these events in the Bay Area and the site plans ones in Seattle, Los Angeles and even one online.

‘Ridiculously Frugal’

But there are some obvious pitfalls behind this strategy, most notably the lack of a paycheck.

Greenberg said her group recommends only volunteering for five hours a week to allow for potential part-time work and job search time.

“You can only job search for so long. You literally can’t fill a whole week sitting at home” job searching,” said Greenberg.

Hoehn overcame the lack of income with some belt-tightening and help from his parents. “I was ridiculously frugal,” said Hoehn, who said he spent an average of $14 a day.

At the same time, there is no guarantee the free work will turn into anything more than just that.

“Work your but off. Keep the faith that you will prove your worth and they will keep you around,” said Dustin Mathews, author of How to Get Rich Working for Free. “If they don’t offer you a position after some time, that’s probably not where you want to be anyway.”

Greenberg said even though there is no guarantee, “We see employers bending over backwards to write them referrals and help them get jobs.”

Legal Maze

And then there are the legal issues, which affect the employers more than the volunteers.

It’s illegal in many cases for companies to employ someone for real work without some college credit, said Michael Casey, a managing partner at the law firm Epstein Becker & Green.

For it to be legal, the training must meet these six Department of Labor criteria: be similar to what would be given in a school, be for the benefit of the trainee, not displace regular employees but work under their close supervision, not give the employer an immediate advantage, no entitlement to a job and an understanding of a lack of entitlement to wages.

Casey said the use of interns or externs is permitted but that it’s essential to have a written agreement that says the individual acknowledges there is no compensation involved, there is no entitlement to a job and that it’s for training purposes.

Even still, Casey said, “We don’t recommend it.”

“We encourage all of our job seekers and companies to abide by federal, state and local laws,” said Greenberg.

Devaluing Services?

Legal issues aside, critics say working for free isn’t for everyone, especially those in the executive ranks.

Cheryl Cavanagh, a managing director at executive search firm Boyden, has advised a number of executives against offering their services for free.

“Once you do that, you’ve devalued your own value from that client. You can’t get that back,” said Cavanagh, who runs Boyden’s U.S. interim management practice. “If they are used to getting it for free, you aren’t going to get $250 an hour for those same services next year.”

Greenberg dismisses this criticism.

“I can’t imagine any employer who would look down on that. It shows they take initiative and how they respond in tough times,” said Greenberg.