What is ‘residual’ income? It is income where you make a sale one time and it generates income on a regular basis going forward. Residual income can even be earned on multiple levels. For example if you refer someone to an affiliate program, you make a commission for a percentage of the initial sale. In the future when your customer pays their membership fees for the program each month, you earn a percentage of that as a commission. With ‘multi-level-marketing’ you may also receive a percentage of the commissions when your customer makes sales of their own.