You can go to websites such as Teespring and design T shirts and you won't even have to print the T Shirt designs out yourself.
You can design the T Shirts through those websites and then have them print the T Shirts out and then sell them to customers and you won't even have to handle the merchandise.
You take the order then pass it onto them and they ship out your merchandise.
Check out https://passiveshirtprofits.com/
as well as Lisa Irby the lady behind the website has great ideas and tutorials on creating passive income while designing and selling T Shirts.