LOL@"magical paperclips"The marijuana always has to be free - no exceptions. P2P nothing of value can be exchanged.
However, what one might also do in order to additionally help patients with their ailments is offer to sell them Blessed Magical Paperclips or Grapefruits for an agreed upon donation amount. For example $45/80/150/280 depending on the holiness of the blessing or the power of the magic.
With that said, you need to be abundantly clear that the transactions are seperate and completely independent of each other. The meds are always free - that is the law.
Magic Beans anyone ?