That's a "recipe for disaster," says Kristin Cadinale, author of "The 9-to-5 Cure." Running a side-business or freelancing on top of an overwhelming workload is one reason to approach this scenario with caution.
Usually, the dual-work plan can only go on so long. At some point, you collapse, drop the business idea or cut the corporate umbilical cord and plunge into full-time entrepreneurship.
Here are Cardinale's tips for juggling your job and business:
Use technology. Consider buying a laptop, netbook or other mobile device so you can get a little business done at lunch or on the bus, ferry or train to and from work. Bring a smartphone along to handle your business calls; don't use the office line.
Tell your boss. Carefully weigh disclosing your side-business activities to your boss. If you're caught moonlighting at work and they didn't know, it could earn you a quick pink slip -- and you want to stay in control of when or if you quit the day job.
Don't overload. Don't exceed your capacity to handle clients for your business, or you'll end up disappointing them. Then you'll be one step farther away from being able to go full-time with it.
Explain your situation to clients. Be open about the fact that you may not be available during normal business hours.
Watch for burnout. You may only be able to keep this up for a short amount of time before you feel like you have no life whatsoever. When the schedule starts sucking all the joy out of living, it'll be time to make tough decisions about which side of your work life needs to go, the job or the business.
Have you juggled a day job and a business? Leave us your tips for how you handled it.