Startup costs for a fashion truck can range from $10,000 to $150,000, according to owners. By comparison, Sarmiento said, "You'd be hard-pressed to open a brick-and-mortar store for less than $200,000."

She said a retail boutique would typically pay rent ranging from $30,000 to $80,000 annually, plus utilities and other costs. That's considerably more than a truck owner would pay for permits, fuel, insurance and maintenance.

She spent $35,000 to get her first fashion truck on the road a year ago. That truck paid for itself within 10 weeks, she said. But she spent more on her second and third trucks, both of which cost upwards of $60,000.

"Now that I have a little more cash flow, I'm investing in a better truck," Sarmiento said of her vehicles, which are old FedEx and bread trucks. Her trucks each have hardwood floors, a dressing room and a generator that allows for lighting, air conditioning and heat.

"We run 365 days a year," she said.

Ray, the owner of Annapolis-based Hobo International, paid $50,000 to buy and retrofit an old delivery truck. She added solar panels to run the air-conditioning and lighting and enlisted the help of artisans to mimic the feel of her flagship store. The truck is painted the same signature blue used for her business' logo.

"We really wanted [the inside] to reflect the flagship store as much as possible," said Ray, who hosted a launch party Wednesday for the truck.

The trucks in the Baltimore area typically target women. Among the varieties are Go-Go's Retread Threads, where Stacey Chambers deals in thrift and vintage wear, and FashN Stop, several trucks operated by Richard Sarmiento, Shelley Sarmiento's ex-husband and a former co-owner of White House Black Market. A new arrival is Lyn Boone, who started her fashion truck, Urban Pearl, this month.

Boone's mobile outfit sells "contemporary, trendy and a little boho," or bohemian, clothes and jewelry — priced from $29 to $125 — out of a Freightliner step van. She drives the 22-by-10-foot vehicle in the Harford County area.

She found the transition to a truck easy to manage.

"There's no additional licensing required to drive it," said. "I don't find it any more difficult to drive than the van I used to have to drive the kids in."

Boone, who used to operate a trunk-show business years ago, worked in promotional sales for the past 12 years.

"I always wanted to get back to something like that," said the Fells Point resident. "It just seemed like the perfect fit. This made a lot more sense. You just drive to people's doors. We absolutely love it."

The regulation of fashion trucks varies by location. Generally, they are less restricted than food trucks, according to Shelley Sarmiento, who operates trucks in three states and Washington.

"You have to do your research," she said. "It's a tri-jurisdictional — state, county, local — thing. Follow the path and get appropriate permits."

Boone said she is mindful not to park her truck near competitors.

"We don't want to park in front of a retail store selling women's clothing," she said. "There's common courtesy with that."

Stevenson's DiMarco sees a lot of promise in the fashion-truck business.

"I call it an online, mobile service," she said. "I think it's better than an online business because it's a very personalized service. That is not a feature you can find online. … Plus, the overhead is not as much as having a brick-and-mortar building."

But she also warns of overexposure.

"Hopefully," she said, "they don't saturate the market with too many all over the place."