I would offer a friendly caution you on using copyrighted images/logos/etc. on your apparel. It is a fast way to get sued. If anyone here tells you differently then I would recommend talking to a lawyer. You said you have a family, I doubt being sued would help you any.
As for wasting materials, how are you wasting them?
As for time, it takes us 1-10 mins to make a shirt using heat transfer vinyl. This would be cutting it out, weeding it, setting up the shirt on the press, pre pressing shirt, and pressing the HTV on. The more you do it the faster you will be. This would be for 1 off designs, but if we are doing a quantity of the same design we cut them all at the same time, weed them all at the same time, and press them at the same time.