Marcus Lemonis, host of CNBC's "The Profit," has a lot of experience with the potential pitfalls that can arise when you share a workplace with a friend or family member. His advice: Don't do it.

"You should never work with your friends or family, if you can avoid it," Lemonis tells CNBC Make It.

That's one of the main lessons Lemonis says he learned while working at his grandfather's auto dealership as a kid and again after graduating from Marquette University. The self-made multimillionaire and entrepreneur now serves as as Chairman and CEO of Camping World, a company with a market value of over $1.8 billion — but, Lemonis started working as a teenager and, he's said previously that his family "ruled with an iron fist."

Working with your family members "usually leads to conflict," Lemonis says.

In his case, he went to work at his grandfather's Miami-based dealership after college. However, Lemonis told Inc. in 2014 that working with his family created an "oppressive" atmosphere. In 1995, after several months of working with his grandfather, Lemonis says he announced that he wanted to enter politics by running for Florida House of Representatives. His grandfather responded by firing him (Lemonis ran, unsuccessfully, as a Democrat, while the rest of his family were Republicans).

So Lemonis knows from experience that working with your family can end badly. "In most cases, they tend not to work out," he says of those situations, adding that the family dynamics can make it difficult to make important personnel changes (though that certainly didn't stop his grandfather). "I don't know how you fire your father or fire your daughter. It usually doesn't end well."

However, Lemonis' own experiences helped prepare him to deal with family-owned businesses on "The Profit," where he tries to help struggling entrepreneurs improve their businesses.