There are many ways to get paid but usually the most popular one is PayPal which I am sure you are familiar with. The vendors can also send you a check in the mail or electronic funds to your bank. There’s not much problem I don’t think in terms of having paid when you promote a product through the vendors affiliate program because they have easy ways of tracking and paying their affiliates.
While these models have diminished in mature e-commerce and online advertising markets they are still prevalent in some more nascent industries. China is one example where Affiliate Marketing does not overtly resemble the same model in the West. With many affiliates being paid a flat "Cost Per Day" with some networks offering Cost Per Click or CPM.
Until 2017, Amazon offered a stepped commission structure so that affiliates who sold a lot of products were paid a higher commission than those who sold little. However, Amazon eliminated this structure and began using flat commission rates for different types of products. While this is likely to continue evolving, examples of the commission structure in 2018 are as follow:
The Program Operator reserves the right to reject any affiliate application if, in the Program Operator’s opinion, that person or entity violates established laws or commonly held standards of decency. For example, we will reject applications from any person or company that promotes any form of violence, illegal activities, or from applicants who the Program Operator prefers not to be associated with. 
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