Google has certain parameters that need to be met before a website can be considered of actual value to Google users. It is outlined in an article in Google Webmasters the way affiliate advertising can be used and how to retain a good search engine listing.
If you have an affiliate website you have an opportunity to develop a residual income. Being an affiliate allows you to earn commission for promoting quality goods and services. All you need is a website or social media profile that will get you accepted onto an affiliate program. Amazon has one of the largest affiliate programs. If fact many well known high street retailers offer commission for website referrals.