I talked to 6 elite matchmakers, and they all said there are 3 red flags they watch for when vetting millionaire clients

John Minchillo/AP Images

A bad attitude is a red flag, according to elite matchmakers.

• I spoke with six elite matchmakers for Business Insider's monthlong series, "Dating Like a Millionaire," about what it's like to date when you're in the 1%.
• All of the matchmakers have vigorous vetting processes to determine whether they should take on a client, from house calls and simulated dates to interviews and investigations.
• There are also three red flags they watch out for: a negative dating history, a bad attitude, and a resistance to the vetting process.
• Visit Business Insider's homepage for more stories.

Money can buy a lot of things, but it can't always hire a matchmaker for a millionaire seeking love.

A millionaire must first meet a matchmaker's standards.

I talked to six elite matchmakers for Business Insider's monthlong series, "Dating Like a Millionaire," and they all said they have a vigorous vetting process before deciding whether they should play cupid for a potential client. The matchmakers work with clients locally and globally, from royals and celebrities to entrepreneurs and CEOs, who have net worths ranging from the low millions into the billions.

The vetting process involves everything from conducting in-person screenings and interviews to background and social media checks. Some matchmakers even pay a visit to the millionaire's house.

They've heard and seen it all - and they can spot a red flag a mile away. Here's a breakdown of what can make or break their decision to take on a millionaire as a client.

A negative history and dishonesty

Patti Stanger of Los Angeles-based Millionaire's Club told Business Insider her company has an intense screening process that looks through each potential client's history. If any data indicates the person might put someone in harm's way, they won't approve them, she said.

Stanger keeps an eye out for restraining orders, lawsuits, institutionalization, and separations. "We don't take anyone who's not legally separated," she said. "They can't be living in the same house."

She added: "If they lie, we revoke the membership."

Read more: The 3 biggest mistakes millionaires make when dating, according to 6 elite matchmakers who help the ultra-wealthy find love

Likewise, Mairead Molloy of Berkeley International in London told Business Insider that when she vets potential clients, she interviews them; asks for a passport, two household bills, and separation or divorce papers; pays a visit to their home; and runs a social media check. If she doubts any of the findings, she hires a private investigator - but gives the potential client advance warning.

Mairead Molloy

Matchmaker Mairead Molloy will hire a private investigator to look into potential clients.

Unlikeability and a bad attitude

Stanger, who turns down 80% of aspiring clients, said anger or bitterness is another red flag - as are unrealistic expectations. She sees many people come in requesting dates with certain celebrities, expressing ageism, or acting shallow.

"They treat people like objects," she said. "Being a matchmaker is probably worse than being a human resource director. We have to take the whole enchilada in."

Narcissism is also a turn-off, April Davis of New York City-based Luma Search told Business Insider. "When someone says there's something wrong with everyone they've dated and everyone they're meeting - they find ways to 'disqualify' people and say they are all the ones with the problem(s)," she said. "These clients think they can hire us and that we'll be able to produce the perfect person for them."

Michelle Rose Sulcov

Janis and Carly Spindel take potential clients on simulated dates.

Ultimately, clients need to be likable. Janis and Carly Spindel of Janis Spindel Serious Matchmaking Inc. in New York City take potential clients, who are men only, on simulated dates to determine just that. That helps the mother-daughter duo get an idea of how much effort the clients put into it, how they treat dates, what their manners are like, and how they behave.

Read more: I talked to 6 elite matchmakers, and they said the biggest difference between dating as a millionaire and an average Joe is also the most obvious one

"We have to like them," Janis said. "If we're going to match someone, they have to be a good guy."

"Life is short," Carly added. "It's important to have clients you like and want to work with. We look for really nice men who would make a great husband and father and are emotionally available. They don't work too much and have time for a relationship; they are a gentleman and would treat a [partner] wonderfully."

Resistance to the vetting process

Amy Andersen of San Francisco-based Linx Dating told Business Insider she has a multi-step method that involves specific questions and in-person screenings. But resistance to the vetting process can be a huge red flag.

Potential clients must complete a form detailing their ideal match. "Someone who cannot complete that in the preliminary stage certainly doesn't have time to be a client or is not making it a priority, which it needs to be," Andersen said.

Justin Colt

For Amy Andresen of Linx Dating, resistance to the vetting process can be a huge red flag.

It's also a red flag when someone balks at the idea of coming in for a meet-and-greet, she said: "Either they don't feel it's necessary or they don't want to pay for my professional time." She added that they need to see the value in the opportunity and that it has to be a "mutually synergistic agreement" to work together.

It makes sense - those seeking matchmaking services want a serious partner who is ready for commitment. If someone can't even commit to the vetting process, how can they commit to a person?