Hiring great people can make or break any business, according to Barbara Corcoran. Cash flow and profits are certainly important. But many entrepreneurs overlook how important people are to their success.

Corcoran believes the most important decisions you make in your life and business come down to deciding which people you let be a part of it.

How to avoid having to fire bad employees

Corcoran invites entrepreneurs to ask her all their burning business questions, which she then answers on her podcast Business Unusual. Lately, she's been hearing from business owners who need to fire an employee who isn't living up to expectations.

What's far easier, Corcoran explains on a recent episode, is to avoid hiring those people in the first place. Be more selective in who you hire. She has a few ground rules in who she'll hire as an employee or work with as a business partner.

Every single hire must have 1 non-negotiable personality trait

Corcoran wants phenomenal people who can rise above their challenges and roadblocks. Even the most successful individuals have experienced their fair share of failure, including Corcoran herself.

She looks for people who can bounce back and keep a positive attitude, despite any setbacks. That's why a key personality trait Corcoran looks for is happiness. It's the one non-negotiable trait for any new hire.

"I learned long ago that if I hire unhappy people," she explains. "There's nothing I can do that is going to change them." Even if someone has all the right resume ingredients to be a top performer, unhappy people will always be unhappy. A single unhappy person can drag everyone around them down. Corcoran has seen it happen early on in her own business.

She's even developed a go-to interview question to weed out negativity and people who complain. In interviews, she asks candidates to tell her about their family. "If their family couldn't give them a positive attitude, there's nothing I can do that's going to change it," she told New York Times.

She also gravitates towards happy people in choosing her friends. People who dwell on their own misery are not the kind of people she wants in her business or in her life.

Listening to your gut pays dividends

Long before she finds out if someone is capable of doing the job, Corcoran asks herself a gut-check question: Do I like and trust this person? She listens to her gut. If for any reason Corcoran doesn't feel like this person is trustworthy, she moves on. No explanation needed.

"When I don't feel right, there's usually a very good reason for it -- even if I can't put my finger on it," Corcoran says. "Our gut instinct is a concentrated dose of our lifetime of experiences. Why shouldn't I trust it?"