Gazrok
A True Doomsday Prepper
I would worry about said gangs assuming that you either A) have a lot of food store in silos/the barn/whatever, or B) set up some sort of forced arrangement whereby you provide food by tending your land and they offer "protection," meaning they won't come try to kill you in your sleep.
If such a gang was too big to tango with, I've certainly considered option B. No such thing as "in our sleep" though, as we'd always use sentries. If everyone in our planned group can make it, would be about 12 of us, so a pretty good number to rotate, even while doing other chores.
Food, water, medical services, mechanical services, and communication services would likely be our biggest trade options. Any gang would be smart to make a deal. (and if they don't, plan C. Poison certain items, bug out to a stash location, wait for it to do its work, then come back and clean up any survivors....trick is to use poison that takes many many hours to work, so more take it).