Brooke Alper and her husband, Josh, not only have two growing children but also a mountain of clothes that don't fit anymore.

Alper of Livingston, New Jersey, said that her closet was bursting at the seams.

"I have a ton of clothes that still have tags on them or are gifts that people give us that you can't return or exchange," said the mother of two boys, ages 2 and 5.

The "Real Money" team learned, however, that with a little work, Alper's closet could become a gold mine.

Moms sell, trade and swap baby clothes for extra cash. How to turn your clutter into cash. Cleaning closets in hopes of a cash payout.

Enter Lauren Lerner, an online-resale specialist from Ambler, Pennsylvania, who said online outlets are the new mega-marketplace. Lerner said she'd made more than half a million dollars since she started selling clothes online a decade ago.

"I see it as green, I see it as money," Lerner said of the Alpers' piles of clothing.

With Lerner's help, Alper was able to convert her family's closets into cash. After selling clothes online for just a few hours a week, Alper has made more than $1,200 in her first year of selling online.

Lerner shared the following money-making tips:

• Snap at least two pictures of the item you're trying to sell online - front and back - so there are no surprises for the buyer. Use a high-quality camera and really zoom in.
• Keep the clothes clean and remember that sizing does matter so be as specific as possible about the fit and fabric. Lerner said to include whether an article of clothing has a tight fit or runs big. Details can reduce your chances of having a buyer return an item.
• Sell seasonal items on resale sites like Tradesy and Poshmark.
• Bundle, bundle, bundle. Sell your clothes by the bagful to save time. Sites like ThredUp and LikeTwice will send you a bag to fill and then they price and sell the items for you. What doesn't get sold is then donated to charity.