If someone wants to start working as an agent with zero investment, which field/sector/industry is better and what are basics of it ?
For this, I'll recommend the two niche markets. Graphic design services and Social Media Marketing or SMM (Online Digital Marketing). For graphic design work, you'll be constantly looking for individuals who want some graphics work done. So you need to decide which services you are comfortable offering and which one's you'll have to outsource. When it comes to SMM, you have to sort out individuals who want help in enhancing their business reach through social media as a tool of marketing. Very straight forward and doesn't require much to get started.