I have thought about it too but dont have the time or space at the moment.....here is my take.
I would look into doing them on your own. There are plenty of tutorials out there on screen printing like on youtube, you would be surprised what you can learn on there when you do a little research. Just buy a screen and some emulsion, and some ink., Make some makeshift equipment with shit in your dad's garage. Get experimental, go abstract, use a paintbrush or stencils, use house paint, stain, bleach, whatever else you can find around the house...Get Artsy with that shit!
IMO Printed shirts that someone had sent out to a shop are a dime a dozen...anyone can draw up something and send it to a print shop.
Personally I am more interested in the craft, the journey and discovery, rather than the end result looking "Professional". Coming up with something unique and interesting doesn’t mean it has to be neat and perfect, but instead fresh, and 1 of a kind.
If you are making them for yourself I think you would get much more satisfaction out of them if you did the process on your own, but it is also a lot more work.