At the very least, he should change needles... I hope you showed him some of the graphics from the above posts, cause he needs to understand that he is taking a terrible risk for very little savings.
I am a financial tight-ass, work contractor and seasonal jobs and often find myself broke as hell (particularly in this tight economy). I pin insulin and HGH sub-q, go through boxes of pins and have never used the same pin twice. Neither do I mix the two substances together to save the expense of two pins. The personal risk is just too great for the very small savings and/or convenience.