It's past midnight, but many staffers at Enplug, an advertising-technology company, are milling about the office in their T-shirts and boxers, writing code and talking strategy. Others are already in bed, sound asleep.

Enplug's office is a six-bedroom, three-bathroom Ranch-style home in the ritzy Bel Air neighborhood of Los Angeles. Twelve of the company's 37 employees, including the chief executive, live and work there.

The idea is to live and breathe work -- 24 hours a day, seven days a week -- without the commute and few outside distractions.

Employees and managers meet, work, eat, clean, exercise and sleep in the same space. And while there are occasionaluncomfortable moments, such as nudging your boss to do the dishes, companies like Enplug say it is good for professional relationships, saves on rent and travel costs and is often just plain fun. Employees who choose to live in such arrangements are generally single 20-somethings who have recently left dorm life.

'We don't try to separate work life from our personal life,' says Nanxi Liu, the 23-year-old co-founder and CEO of Enplug, which creates digital billboards, incorporating tweets and other social-media streams. 'It's a little bit cultish,' she says. 'It is also extremely efficient.'

At the Enplug house, work literally gets done around the clock. Engineers often pull all-night coding sessions and roll out of bed around midday, while account managers wake up hours earlier to attend client meetings that are typically held offsite in cafes or clients' offices.

'We work 24/7. We code. We go to bed. We wake up. We code,' says Alex Ross, 23, the firm's chief technology officer and one of Ms. Liu's roommates.

Enplug's five co-founders, most of them recently out of college, started rooming together last year to save money, working out of their apartment -- a familiar scenario for many startups.

But as the company grew, they maintained their live-work arrangement. Instead of renting a separate office space, the Enplug staff simply moved into a bigger house.

Most of the staffers living in the house get paid a modest stipend in lieu of salary, while the founders forgo salaries altogether, funneling company earnings back into rent, utilities and large boxes of Cheerios. Chores such as housecleaning and dishes are shared among the roommates and a maid comes in once a month to clean, but there are basically no formal house rules.

Two Enplug employees got married to each other just weeks before moving into the house in November.

'We were a little skeptical living together with lots of people in the house,' says Bruno Denuit-Wojcik, who moved in with his wife Justyna. The couple, both Enplug software developers in their 30s, say the practical perks, such as free food and rent, make up for the lack of privacy.

There are no data available on the number of companies where employees live together on-site, but Nancy Rothbard, a management professor at the University of Pennsylvania's Wharton School who has studied boundaries among employees, says that these closely tied firms face many of the same challenges as family businesses. 'The boundaries become very blurred,' says Dr. Rothbard. 'If you have a bad day at work, the good news is you can talk about it with someone who can understand. The bad news is you can't just detach.'

Meanwhile, commercial ventures are cropping up to provide co-housing spaces for startup employees.

CrashPad, which launched this spring and now has three houses in the Boston area, offers tech workers communal living spaces where they can sleep, share a kitchen, get some work done during the day and schmooze about startup life.

Would-be residents must apply -- there is a waitlist, says co-founder Jennifer Fremont-Smith -- and are selected with skills diversity in mind, mixing coders with marketing experts and designers. CrashPad's co-founders recently received venture-capital funding to expand the co-housing concept into other cities.

The houses are furnished and include private 'cloffices' -- small closet-size offices -- allowing residents to brainstorm. The rent typically is about $1,200 a month per person and residents are only expected to stay for three or four months, until their startups get off the ground.

Steve McGarry lived in the CrashPad for three months starting in March after moving to the Boston area from North Carolina. Within three weeks of moving in, Mr. McGarry started a company with his new roommate and met a key business adviser at one of the house events.

It isn't just startups that are co-housing employees. At Whirlpool Corp., sales trainees live together for about 10 weeks in the 'Real Whirled House,' inspired by MTV's 'The Real World' reality show.

Sales recruits share an eight-bedroom, eight-bathroom condo complex in St. Joseph, Mich., that is filled with Whirlpool brand appliances as well as products from competitors. Residents cook, clean and entertain clients and colleagues together. The idea behind the program is to immerse recruits in an appliance-rich environment so they become experts on the products they'll be selling, and to bond with their colleagues.

Allison Gillespie, who completed the program in 2004 and now helps run its alumni group says that the company wants recruits to have hands-on experience.

There can be awkward moments when staffers live together.

FiveStars Inc., a San Francisco customer-loyalty service that employs about 100 people nationwide, rents houses in cities across the country, including Denver and Los Angeles, in which staffers can work and sleep.

Last year, FiveStars CEO and co-founder Victor Ho, 27, and his roommate Eric Burdullis, 25, the company's head of operations, were giving each other performance reviews on the living room couch in full view of their colleagues, some of whom are also roommates.

At the end of an intense two-hour conversation, there was no place to retreat, so the two 'ended up back on the couch with a beer,' says Mr. Burdullis. After that, they decided to take future feedback sessions to a nearby bar.