One of the most widely-available ways for making money is to drive for Uber or Lyft. The sharing economy has quite literally exploding, and both Uber and Lyft are at the forefront. The best part? You can turn on and off your availability through these networks with the simple click of a button, effectively allowing you to make money no matter what time of day or night it is.
I surprisingly get a lot of people asking to detail their car. I never intend to make a business of it, but I love doing it to my cars and people ask me to do it to theirs. All it takes is a cheap orbital buffer (mines a used craftsman) and a shop vac. I normally get easily $100 for a basic wash/wax/vac, or $200 to remove scratches and polish then wax the car.