You will need to start small. If you have a garden use that to raise some chickens from scratch. If you don't have a garden, make a deal with a farmer to use some land to raise chickens. You can sell some of the eggs and use others to get more chickens by letting them hatch.
Protecting the chickens will be a major issue in the beginning.

Alternative is to raise money to rent land and build coops and get an initial amount of chicks.