i am going to start designing a website for a client that sells her art trhough the website and wants me to add some affiliate link so others can have an account and sell, and get comissions for it. what should i do, where to start to build this?

also, the client wants to have a shopping cart, which i prefer not to use paypal since it is needed to send newsletters and autoresponders. i know there are some companies that provide all this together, so any recommendations are welcome.

thanks in advance for both answers.