When people have had enough training in the courier sector, they prefer to earn money as self-employed couriers part-time. This way, they can earn double income. Self-employed services may not pay well initially, but they can flourish over time. As the business grows, you can change your method of transport from maybe a wagon to a delivery service truck and slowly own a fleet of delivery trucks service. It will increase the amount and weight of packages you can transport and earn more.