Do you enjoy fast food or going into retail shops? Many companies hire mystery shoppers to test the customer service of their stores. A common one is Subway, which hires mystery shoppers to ensure that "Sandwich Artists" are following all the franchise guidelines. If you have time and can travel to different places, this could be a good side hustle.
Two-tier programs exist in the minority of affiliate programs; most are simply one-tier. Referral programs beyond two-tier resemble multi-level marketing (MLM) or network marketing but are different: Multi-level marketing (MLM) or network marketing associations tend to have more complex commission requirements/qualifications than standard affiliate programs.
Websites like Survey Junkie will pay you a decent chunk of change for the low-maintenance, borderline mindless task of completing surveys. Companies want to understand consumers better, and one way they do that is by compensating survey-takers (a.k.a. you). Most surveys pay between $0.50 and $1.25, and many of them take less than 5 minutes to do. You can read our full Survey Junkie review for more info.