I would definitely invest in a fence before getting chickens. You might look on Craigs List and Freecycle for old chainlink fences. It is difficult to free range your chickens and expect they will remain on your acreage at all times. Your neighbors could point this out as your not containing your pets, as well. Good fences make good neighbors!
I also think the nice note is a good idea, maybe with a P.S. like "Maybe we can all have the benefit of some fresh eggs soon if everything goes well with our chicken investment." A hint of egg sharing, or supplying, along with the implication that you have made a monetary investment.
I scrounged and scavenged and got a complete fence around my 1-2 acre lot here (part of which is old chainlink) and I think it keeps out the casual dog or coyote. Then I have my dogs in the largest portion, on above-ground electric containment. I dare any predator to walk into the danger zone....if they succeed, they are welcome to a chicken nugget! They've earned it! The chickens free range with contentment and safety and I don't have to start anything with the neighbors.

I scrounged and scavenged and got a complete fence around my 1-2 acre lot here (part of which is old chainlink) and I think it keeps out the casual dog or coyote. Then I have my dogs in the largest portion, on above-ground electric containment. I dare any predator to walk into the danger zone....if they succeed, they are welcome to a chicken nugget! They've earned it! The chickens free range with contentment and safety and I don't have to start anything with the neighbors.

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