WHEN CANDICE BENNETT lost her job selling cars in Las Vegas, she tried to figure out new ways to earn money before moving cross country.

Ms. Bennett, 29 years old, who has yo-yoed between a size 6 and 22 over the years, realized she had accumulated a lot of clothing in a variety of sizes and decided to try to sell some. To make her sale look professional, she turned her guest room in Henderson, Nev., into a boutique selling her old evening gowns, business suits and jeans. She replaced her exercise equipment with a full-length mirror and a chair and arranged her merchandise by size in the closet. Then she posted an advertisement on Craigslist: "Forget paying store prices, come shop in my closet!"

To sell her old designer clothes, Tory Shaheen has tried to make her Manhattan studio apartment feel like a boutique.

"I wanted it to look as legitimate as possible -- to take away the fear of 'Who is the strange person wanting to sell her clothes?'" Ms. Bennett says.

Many women have been shopping in their own closets lately, digging out old styles as a way to avoid buying anything new. Now, some enterprising clothes horses who splurged on designer clothes, handbags and shoes over the past several years are turning their closets and homes into secondhand stores. They are rearranging their rooms to resemble store dressing rooms and buying industrial shopping racks. Some are offering up wine and bottled water to their few customers, and others are acting like personal shoppers full of fashion advice.

Such glorified garage sales, which feature everything from $5 Ann Taylor pants to $30 Miu Miu sweaters and $100 studded 7 For All Mankind jeans, are being promoted on neighborhood posters and on Craigslist, a Web site with free local classified listings. Craigslist says its "clothing & accessories" category had 715,228 postings last month, more than double the 356,162 it had in the same month last year.

Closet boutique owners are finding they have many of the same problems as regular retailers, and then some. Genna Snajkowski, 21, who implores strangers on Craigslist to "come shop in my closet! Literally," spent hours ironing her too-big Lane Bryant plus-size clothes before putting them up for sale earlier this year on a hanging rack in her Deptford, N.J., living room. Her first five customers made a mess looking through the clothes, she says, picking out merchandise, dropping it on the floor and throwing it back on top of the rack, leaving her to straighten up afterwards. "They don't really care -- just like at a regular store," says Ms. Snajkowski, who has made about $60 so far.

Roxanne Scacco, a 34-year-old technology support specialist in San Diego, decided to open up her closet after overhearing women in stores complain about high prices. Instead of dropping off her old clothes at a consignment store, she decided she could sell the items on her own for the same amount of work and make more money.

She quickly learned that the sales are more fun -- and it's easier to move more merchandise -- when she offers up fashion tips to customers, such as how to mix and match her clothes. "I know the stuff. This is what I used to wear," she says. Her advice, she says, helped persuade one customer to buy a scarf, along with some other items. "I'm their personal shopper," she says. "I find myself giving advice, which is really surreal."

The private sales often compete directly with consignment stores, which aren't always thrilled with the new store in town.

"People are now trying to move it on their own and eliminate the middleman," says Raz Damas, a saleswoman at the Refinery Celebrity Resale Boutique, a high-end consignment store in the Las Vegas area. Ms. Damas says an increase of such direct sales over the past year may be contributing to a decline in her business, which takes a 50% cut for selling castoff clothes.

Closet owners also have to grapple with one of retailing's biggest downsides: the possibility of returns. To sell her old clothes from designers like Prada, Coach and Versace, Tory Shaheen, 33, who works in the pharmaceutical industry, has tried to make her Manhattan studio apartment feel like a nice boutique by first dry-cleaning all the clothes before putting them on display in the closet. Ms. Shaheen also offers her customers wine, beer or bottled water and throws in extra free items to her best customers.

In January, her first customer, Georgia Redd, browsed for about an hour, enjoyed bottled water and spent about $160 to $180 on 20 items, including a $20 Oleg Cassini dress, a $20 Ann Taylor suit and a $20 Banana Republic blazer. Ms. Redd says she bought them all for her adult daughter who worked in finance and is the same size as Ms. Shaheen.

The next day, however, Ms. Redd contacted Ms. Shaheen, who had also thrown some extra sweaters into the deal, to say that her daughter didn't want the second-hand clothes. "I was not about to offer that she could return it," says Ms. Shaheen, who specified in her "Private Clothing Sale" ad that all the cash-only sales were final. She says she goes out of her way to make the experience as pleasant as possible for her customers. "I gave her some absolutely ridiculous deals."

Ms. Redd, 65, an artist in Brooklyn who says she never buys anything new, says she didn't want to return the clothes. "It was a great deal," she says. She now has all the clothes in a box, in case her daughter changes her mind. "I'm hoping she'll come around," she says.

Return policies aren't the only ways that private sales differ from the traditional rules of retail. Destiny Turner, 23, held a sale in her closet in Walla Walla, Wash., before moving to Hawaii. One of the customers, her co-worker Annaliese Shafer, wanted to buy an ivory J. Crew coat from a "maybe for sale" area of the closet. Ms. Shafer tried it on, loved how it looked and asked Ms. Turner why she would sell something so attractive.

"It was cute, and I wanted it," Ms. Shafer said. Ms. Turner then decided to keep it.

Write to Jennifer Saranow at jennifer.saranow@wsj.com