Worst business
I has several business and the worst one was a mobile auto service repair. I wound up specializing in returing cars from the dead, and working on a lot of completely abused cars. I gave up pretty fast. Sadly most people out there do not even change their oil. I worked on one car that the electrodes on the spark plugs were completely gone. I rebuilt a guys van and he refused to break in the engine, popped the clutch hard to screech the tires all over town and blew the engine in less than 2 weeks.
I had a landscape and tree trimming company with my oldest brother as my partner, and that worked out really well. We each had our own accounts, covered each other on vacations or if we were sick, and did big jobs together. I wound up giving him all my accounts when I transferred to a university in San Diego to finish my bachelor's degree in engineering.
Also, the worst part of having your own business is self employment tax. 15% right off the top. That is a big bite out of the income.