Merch by Amazon is an on demand t-shirt printing service that allows you to upload and sell your t-shirt designs on Amazon for free. All you have to do is upload your design, set your price, pick a few t-shirt colors, and submit the design. Merch by Amazon takes care of the rest. With Merch by Amazon, you'll get paid a royalty on each t-shirt that you sell. Some of the links below are using affiliate links from trusted websites.
You can request an invitation for Merch by Amazon here if you aren't a member.