Working in a big glass skyscraper in the Financial District is fun, but working from home creates less expense.

Food

If you buy your lunch, it’s easy to spend $5, $8, $12, or more on a single meal. Working at home allows you to make a quick sandwich or eat last night’s leftovers. For most people, it also provides an opportunity to eat a healthier diet.

Even if you run out to grab soup or a burrito once or twice a week, you can still save at least $15 a week by eating lunch at home. That’s $780 annually. And that doesn’t count those coffee runs with your coworkers, which are really nothing more than an excuse to get away from your desk.

Commuting

Unless you walk or ride a bike to work, which only a small percentage of people actually do, commuting is proof that it takes money to make money.

With the cost of public transit, let’s just assume for the sake of argument, that the minimum cost for commuting to work every day is $5. I can assure you it’s more likely to be twice that amount for most people, but even at $5 a day, that translates to $1300 a year.

If you drive a medium sized sedan, and put 10,000 miles a year on it, then according to AAA’s Driving Costs for 2009, your total cost per year is $7,022. (That factors in fuel, maintenance, tires, insurance, license, registration, taxes, vehicle depreciation, and finance charges.)

If you work from home, those costs will plummet. Be sure to contact your car insurance company to let them know about the change.

Child Care

I know several stay-at-home dads and moms that work from home. Well, maybe they are really working 2 full-time jobs at the same time. But doing so let’s them enjoy their kids (most of the time) and save the expense having to pay for  daycare or sitters.

Taxes

If your home office is the primary location for most of the activities associated with your work, and you make use of it regularly, then you use it to take a tax write-off. Likewise for any computers or other gadgets that might be required to do your job.

Clothes

Some of us, ahem, may not be the sort to ever dress too flashy. But, in some jobs, the employer or the corporate culture may mandate the need to dress in a certain manner. For instance, working as a stock broker, you might need to wear a suit everyday. If you work at home as a day trader, there’s no need.

You may still need a nice suit or three for meetings and other work-related events, but you won’t need a full wardrobe of work-only attire. More than one great startup has been launched by people working in their boxers.

Health

If you’re working in a more relaxed environment, eating better, and working out more since you are saving on commuting time, then you’re likely to suffer through fewer colds. As your own employer, time is money, so staying healthy saves you in money lost to unproductive hours.

Now, working at home isn’t for everyone. Some people need more direction. Also, if you’re a mechanic, its a little hard to run a business out of a spare bedroom. Other people simply need to be in a busy office to feel useful.

But, if you can work at home and maintain the same income level, then you’ll save money and come out ahead.