Founded in 2011, Menlo Park, California-based Poshmark is the fastest-growing mobile marketplace for fashion. The company's app allows its community of users to sell clothing from their closets using only a smartphone. Starting with just three users after its launch, it now has a network of 350,000 closets and has sold 1.5 million items of clothing and accessories.

But co-founders Tracy Sun and Manish Chandra say during an Inc. Trep Life mini-documentary that the road to growing and securing millions in funding has been a hard one. Today the company boasts over $15 million in venture capital from Menlo Ventures, SV Angels, Inventus Capital Partners, and others, but trying to get the first investment was an uphill battle in the male-dominated tech world.

"The grind from day one was convincing other people that the idea was valid--that fundamental parts of the business [were] valid. I happen to be in a world that is run by men and yet Poshmark is all about women. The grind was talking to the umpteenth investor or team member who all said, 'I don't understand why women would want to sell things from their closet. I don't understand women,'" Sun says. "You're not supposed to get women. It's women who are supposed to get Poshmark."

To find out more tips and hear the rest of Poshmark's story, watch the video below.