I don't know how many t-shirts you are planning to order, but for around 30 t-shirts (regular short sleeve, cotton, only 1 ink color), you can get them for around $10-$11 each from ClassB. That's a fair price, especially when they don't charge for artwork, a setup fee, and free shipping for orders over $50. Of course, their prices depend on the total number of shirts that you order, so more shirts = cheaper price per shirt.
ClassB is easy and decently priced. We use them. Super easy to design and print with them. Not quite as cheap as a local printer. We use the tech shirt material because the boys like them and they are very comfortable and look nice.
Technically, any BSA trademarked imaging can only be reproduced by licensed partners like ClassB. I doubt any local printer would care but that is the legal limitation. Some printers may balk at printing them.
That's broadly the idea. It seemed like one of those if not now then when moments.
Fact is that most writers don't make enough to live on but if I don't give it a go I'll never actually know whether I could do it or not.
My guide (who, like me, had visited Old Economy in childhood but oversaw multiple restorations since then) was walking me through the common house, and I told her that I vaguely recalled that one of the rooms held a vintage flea circus. Her eyes lit up, and she exclaimed "I remember that, too!"
Restored a childhood memory ... daily good turn done.