"There is no free lunch," according to Ira Fateman, a San Francisco certified financial planner. "It's one of the few things that are true in life."

And it's almost as certain you will get a similar response if you ask most financial advisors about free investment seminars that offer to provide attendees with a no-cost meal. To say that free-lunch investment seminars are viewed with skepticism would be an understatement.

There is some justification for this. When the Financial Industry Regulatory Authority (FINRA) examined more than 100 free-meal seminars, it found half of the invitations and advertisements contained exaggerated or misleading claims, and 12% appeared to involve fraud.

Chances are good that the average person will receive an invitation to one of these dubious opportunities, FINRA reported after surveying investors. "We found 64% of respondents over the age of 40 had been invited to some sort of free meal investment seminar," says Gerri Walsh, senior vice president of investor education for Washington, D.C.-based FINRA.

The problem with many of these seminars, Walsh says, is that they are more focused on selling investment products than on educating investors. Often the hard sell doesn't come during the seminar, she adds. "It comes afterwards," Walsh says. "The organization will send someone to your house or send an email and start pitching products."

Free investment seminars are one of the most effective marketing tools available to investment sellers. One marketer's website suggests that a $10,000 investment in seminars is likely to attract 40 attendees, of which four will make a purchase at an average commission of $7,500, producing a 300% return on marketing investment.

Free seminars may be used to pitch a variety of financial products, but they are commonly associated with annuities, Walsh says. These often have high commissions, as well as other features that make them unsuitable for many investors, she says.

FINRA suggests checking invitations for specific claims, such as helping attendees to retire early, generating investment double-digit investment returns and being able to receive as much income in retirement as from working. Walsh also advises looking at the backgrounds of presenters and sponsors, using FINRA's BrokerCheck tool and checking with state securities regulators for complaints or disciplinary actions.

While Millennials are less likely to be targeted than older savers, that doesn't mean they can't be affected. "If they hear about their parents going to these kinds of seminars, they maybe should be a bit worried about whether their parents are getting a hard sell," Walsh says.

Of course, only a minority of free financial seminars suspected of being fraudulent. And free seminars can be useful. "I have attended some seminars at which I actually learned something valuable and was not faced with sales pressure after the fact," says Barry Korb, a CFP with Lighthouse Financial Planning in Potomac, Md.

Korb says good sources for unbiased finance seminars include those sponsored by university agricultural extension services and community colleges. Considerable online information is available from FINRA, public libraries, the federal Consumer Financial Protection Bureau and private groups like the National Association of Personal Financial Advisors. FINRA says seminars offered by employers are also less likely to be suspect.

Pay a little for education can gain a lot in terms of unbiased advice, says Fateman. He recently began offering a $195 seven-hour finance seminar in connection with San Francisco State University. No products are sold during or after the seminars, Fateman says, although he is hoping to create relationships with attendees and eventually get them to attend additional seminars.

Meanwhile, Walsh says that investors are encouraged to want to learn. "But be skeptical," she says. "Make a pact with yourself that you are not going to sign up for anything or open a new investment account until you've had time to distance yourself from the free meal seminar and think about your choices."