It's an excellent retirement project for elderly persons who want to keep busy and supplement Social Security, pension or other income. Many of the most successful earthworm hatcheries are owned and operated by women.
Earthworms are amazingly prolific breeders.
A thousand mature breeders, properly cared for and allowed to multiply may give you half a million or more breeders, growing earthworms and egg capsules within a year. So that you may begin to sell in volume during the season following your start, it is advisable to begin with as many breeders as you can conveniently handle. The development of your project will seem slow for the first two or three months, but don't be impatient. Soon thereafter it will begin to pyramid rapidly. Don't begin selling too soon, because you won't want to sell too many of your breeders at this stage, but after six to nine months your pits should be well-stocked and you will be able within a short time to realize many times your initial investment.