Both these companies allow you to design products and then print them on demand for your customers as they order.
You have no outlay for stock and processing of orders and your sales commissions are automatic. You can create a store for a product line and leave it alone to fend for itself or you can maintain it for the long term and drive customers to your store via blogs and other websites.
Commission is generally paid thirty days after a purchase. This allows a customer to return an item that they don't like, for any reason, to zazzle or cafepress.
After the thirty days your account is credited with the commission, which you can set yourself or accept a default setting from both companies.
Another way to gain revenue with zazzle is to become an affiliate who sends customers to other peoples stores. You install a link to a store with your personal code incorporated in the HTML any purchase that that prospective customer makes will then give you up to 15% commission. Plus as you send more traffic you can receive additional bonuses up to 17% all this on top of your own agreed mark-up on your products.
So if a customer goes to your store through your link b8ut doesn't buy your product. Instead they go to another retailers store and purchase you will get the bonus plus commission for directing the customer.
While Amazon's affilliate program is more popular. zazzle.com's affiliate program does give you much higher returns percentage wise and also gives you two extra and well paying ways of earning cash.
I would say try out zazzle.com and see what you think.