Referral links are a great way to make money from visitors to your brand, by posting links to products or service that are relevant to your brand this can be useful for your users to show them products and services they will be interested in and also allows you to earn a fee for referring them.
Most established companies offer referral links through affiliate schemes, these can be found by searching the company name followed by affiliate.
Each affiliate may offer a different payment scheme some give a flat fee for each users you sign up and others give a percentage of earnings from the user you sign up. Be sure to read all the terms and conditions of the affiliate schemes you choose to use as if these aren’t followed you may not get paid and make sure the brands you promote are relevant to your own brand.
There are also affiliate companies who handle affiliate schemes for multiple companies which can be useful for finding affiliate schemes. One is CJ Affiliate (formerly Commission Junction).