If you know something and it is valuable to other people, you may find that consulting is a profitable home based business. Since you will be traveling to your clients, there is no need to maintain a fancy office or hire a secretary.
Of course, an advanced degree or lots and lots of experience help here. It is unlikely, for example, that a new business school graduate would get many gigs as a consultant. However, if you’ve been doing something for a long time, you have a lot of experience to pass on to companies and individuals who are willing to pay for your expertise.