There are some niches where you can invest in some $100k equipment and then basically just lease it out to people, or operate a very simple business where all you do is operate the equipment.

Some examples: - cutting prescription lenses - power washing/landscaping equipment - food carts - printing T-Shirts - plotters/CNC machines/3D printers

I know a few people who run side businesses where all they did was buy the equipment and hire one employee to operate it.