In the scenario you envision you're going to need a high quality fence. Someone starving with kids to feed would make short work of any organic matter separating them and a bushel of apples. 10k for 3-5 acres is going to be hard to find. Unless your ok with it being pretty remote. If that's the case how do you manage land so far away?
I have about an acre that I'm creating as a sort of food safety net for my family. The land is 2 hours away which makes my management of it tricky at times. Often when I am there I think about the what if's of the future. The only way I can envision keeping my landscape secure is with neighbors buying into it. If you give your neighbors some of the harvest or let them pick on occasion, they immediately become shareholders in your edible landscape. They would then have a vested interest in keeping away any would be thieves. Of course the flip side is what happens when they tell all their friends and extended family about their access to your land

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