Having no experience in such matters (except that one college experience that ended badly), I would think that even in a SHTF society, this would be far to dangerous to contemplate doing (dealing with the roughest lawless of customers). But.... remember we are talking survival here, so nothing is off the table if you have kids to feed and have to "bring home the bacon". Yes, I am sure even I (who has been labeled a "drug warrior" a time or two on FR in the past) would think twice if it looked to be an form of income in rough times. But it would have to be a last resort... enough said, we all can picture what it would take to strip us of our pride to do something we would otherwise never do.
Prescription drugs are what I worry about the most to be honest. I need a blood thinner and heartburn meds daily and I don't have a source to manufacture alternatives on my own. I know that I would have to venture out there into that horrible dysfunctional crazy world and trade for it or hope to be in a free for all at the beginning raid of prescription stores when they were robbed. It makes me cringe just thinking about it.
I've just thought about this...if you are on blood thinners now, can you start noting the color of the blood they draw from you for blood thinner levels?...like have them place a tiny drop on your finger, and see if after time you can guess what your numbers are going to be...like if you blood is very dark, or very light or seems think of thin....perhaps in a SHTF scenario, you could develop your own way of determing your dose....