Using trade discounts vs affiliate links
As a designer, you can choose to apply to either trade programs or affiliate programs to earn extra on every product you recommend to your client.
If you have a trade account with a vendor, they will give you a discounted price on the item. You can then add your mark-up to that item to create a custom price for your client. If the client approves the product, you would then order the product on behalf of your client. You purchase the item at the discounted rate from your vendor and you earn the mark-up amount you charged your client.
If you don't want to be in charge of ordering the product on behalf of your client or dealing with any product returns, you can choose to use affiliate links instead. In this case, the client shops the item retail, and you simply earn a commission for facilitating the sale.
Here's how it works
When you join an affiliate network you will get access to a long list of retailers that have affiliate programs within the network. You can pick and choose which vendor programs you want to join. Each vendor offers a different commission rate (the average is 7% or 8%). Once approved, the retailer provides you with an affiliate link for every product. You would then take the affiliate link and add it to the product in your product library by editing the product details and adding the link in this field.
If you use that item in a project, and then the client clicks on the shop button and goes to the vendor's site to purchase the product at the retail price, you will earn a commission for facilitating the sale. The network will then send you monthly payments for all the commissions you have earned.
When determining whether to use a trade discount or an affiliate link, it really comes down to how much you want to take on. If you just want to allow the client to shop retail and earn a commission, you can choose to sign up for affiliate programs.
If you want to use trade accounts and include a mark-up on the price of the product, this means you would be responsible for managing the ordering and delivery of the product and you would need to handle any cases where the product needs to be returned.