Believe it or not, in this age of virtual economies, not all businesses have much in the way of major business expenses – at least not in terms of infrastructure.
I once worked part time for a company that did all of their work online. All the workers communicated via instant messaging, and the employees were scattered in different places across the United States. Of course, they had expenses in the way of money they paid to employees, but that was covered under an existing revenue stream.
Online service businesses are unique in this regard. You can work as an independent contractor providing all of your services online, such as being a web developer or freelance writer, and the only expenses for business operations of this kind are your Internet connection, usage of electricity, any online advertising and depreciation of computer equipment.