This requires transportation. If you live within a few miles of work you could walk, but most people don't. They need to drive or take public transportation. This takes money. Not only do you have to consider the cost of fuel for a car, you also have to consider the cost of the car, maintenance, and insurance.
Many jobs require a certain standard of dress.
This means that you may have to buy specific clothing for your work. A Uniform is an obvious type of job-related clothing, but so is a business suit. If you work more than a few days a week you need to have several outfits. These costs add up. Finally, another consideration is the amount of money you will have to spend paying other people to do the things that you don't have time to do because of your job.