It's entirely normal to pitch in with people and share stuff, borrow stuff or have stuff borrowed from you. As long as everybody get their stuff back it should all be cool.

If it's a survival situation or gearing up for one and peripheral can't or won't pitch in together and act as a family in a lot of ways, then that's definitely not the people to get involved with a survival retreat on.

Likewise, if your family won't do that or fly with it, then there comes a time to make some very sober decisions about how seriously you are going to take it and where that investment goes.

It's a given that for every serious survivalist in these things, there are going to be a few "passengers", but the real survivalists are the ones most likely to carry the day and you deal with the "passengers" on a case by case basis.

One of those issues with contiguous parcels is that parcel subdivisions are not always possible or practical in a lot of areas. That's especially true in a lot of the areas where survival retreats are getting built and you need some control over who your close neighbors will be.

In that sense, it is definitely a danger point if "the family" suddenly doesn't like you or recruited your efforts on false pretext, or contrives excuses to rob you. The old Masonic and guild networks in Europe along with the Jews of Europe had to contend with that sort of thing all of the time. Non Muslims living in places governed by Sharia law have to deal with it.