Becky O’Neil of Arlington, Va., remembers her first Christmas as an entrepreneur: She worked the entire day.

It was 15 years ago, and O’Neil had just started a dog-walking service, called Becky’s Pet Care. As a new mom, she had tired of logging long hours at a medical office, where she worked as an X-ray technician. “I needed something a little more flexible in my life,” she said. Having grown up on a farm, she decided that an animal-related business made sense. Most of the time, she figured, she could walk dogs with her 7-month-old son, Patrick, strapped to her back.

What she hadn’t realized is that flexibility can come with a cost. Getting her start-up off the ground required long hours, hard work and unwavering commitment — even on Christmas Day.

That first holiday as a solo entrepreneur, O’Neil started her day at 4 a.m., tending to clients’ pets for four hours straight. “I was home by eight to open presents with my son, spent an hour there opening gifts, went out and worked all day, came home at 4 o’clock to have Christmas dinner with the family, and was there about an hour again, and then went back out and finished my visits,” she said. In all, she took care of about 25 pets.

But the marathon work day didn’t dampen O’Neil’s entrepreneurial spirit. If anything, it fueled it. “I was so excited to have a lot of business, and to be earning money, and to see my business was credible,” she said. “It was a great day.”

O’Neil now has two locations, in Alexandria and Woodbridge, and has built something of a dog-walking empire in Northern Virginia. Her company employs more than 125 people, serves 3,000 active clients, and this year expects to post $2.3 million in annual revenue. Please note the business has grown since the accompanying video was produced in 2012.

Her family has grown, too: Son Patrick is now 15, and daughter Peggy is 13. The original plan to walk dogs with a newborn worked, at least to an extent. “I could put him in a backpack and walk dogs in the sunshine,” she said. But she still needed to put her son in day care when she needed to focus. “Having never owned a business before,” she said, ” I didn’t realize how long the hours would be.”

Within months of starting up, O’Neil was juggling so much that she needed to hire her first employees. She credits the company’s rapid growth to good timing — pet sitting was just starting to take off — and customer service. Over the years, Becky’s Pet Care has been cited by Angie’s List, Washingtonian and Pet Age magazines; this year, it was named “business of the year” by the National Association of Professional Pet Sitters, a nonprofit trade group.

Today, many of the dog walkers and pet sitters that O’Neil hires are moms themselves, who drop their children off at school and report to work. All pet-care providers must pass background checks, and O’Neil has established a lengthy hiring process, consisting of a phone interview, an in-person interview and then a field interview (“We see how they are with a dog,” she explains), to ensure good workers.

Her basic service — taking care of pets while owners are at work or on vacation — has changed little over the years, and neither have the challenges. Managing keys, dealing with inclement weather, and battling D.C.’s famous traffic remain headaches, although “we have definitely improved our systems over time,” she said.

For instance, her staff now follows an emergency protocol — from spraying WD-40 into a sticky lock to calling a locksmith — if a key doesn’t work and Fido (on the other side of the door) is howling. An operations manager handles the day-to-day scheduling of clients. Another manages all the pet sitters. There are procedures in place for organizing clients’ keys, training new walkers and finding backups when pet-care providers call in sick. As a result, O’Neil is considering opening a third location in the year ahead.

Still, she said, entrepreneurship is far from easy. That first Christmas, “I was terrified it wouldn’t work out,” she says. And while the business grew quickly, it was three or four years before she paid herself a salary. “There were times when I lived on credit cards,” she said.

But she recommends it, especially for parents who desire flexibility. “It’s absolutely a wonderful way to change your life,” she said. Over the years, she’s adjusted her schedule to attend her children’s events, take field trips with them, or be there when they’re sick. “Having Becky’s Pet Care has allowed me to spend a lot more time with my children, although there were times when the business encompassed all of me,” she said.

These days, O’Neil personally spends less time walking dogs and more time shepherding her company’s growth. This year, she’s not working Christmas — the spoils of a successful entrepreneur. “I will have walkers out working,” she said. “I just won’t be one of them.”

Instead, she’ll be cooking dinner at her aunt’s home, tending to her black Labrador Retrievers and exchanging gifts with her kids.