Amazon Merch is a program that allows you to sell tee shirts on a “print to order” basis. If you sell one, they print one. Come up with your original idea, upload the file, and off you go. There is a wait time and an approval process first, however.
AMAZON MERCH APPLICATION PAGE ➜ https://merch.amazon.com/landing
MY CURRENT TEE SHIRTS ➜ http://amzn.to/2hUTU1i