Short-term income is made from the sale of the product/service. Long-term income is made from recruitment.
In retail, some companies have a great product and they can afford to make it, package it, house it, advertise it and sell it at the point of purchase.
Other times, companies have a great product--without a distribution system in place. In that case, the retailer will use network marketing as the distribution system.
Know that network marketing is like any other type of business--profits depend on number of leads, conversion rates and profit margins. The only difference is that you are also looking to recruit others into the organization. Your long-term income will also depend on leads, how many of those prospects you convert to distributors and the percentage payout for your "downline."
All the best.