I have had experience with this: a neighbour had a knock on the door one day and an agent asked if they were interested in selling? answer was maybe if the price is right & the rest is now history; I have a new neighbour & old neighbour moved & downsized! (this street has only 1 acre blocks in the cul de sac)
So I would say just go straight to the source if it is the owner not a tenant of course.
I tried this many years ago with a a couple of properties I saw as potential subdivisions, although I never let on about my interest in subdividing, just sung the praises about the property and the location.
I personalised letters to Owners of two neighbouring properties that I was interested in by searching Owner details and using names in the letters, not just a generic letter box drop.
Although I didn't achieve a successful purchase, I had a very promising written response from one Owner soon after who had moved interstate and who had been keen to sell the property several months earlier but had since leased the property out and now wasn't the right time. My timing was just a bit off.
The neighbouring property Owner also did respond with a a gruff "they would have to carry him out in a box", however, he obviously kept my letter and contact details because about 5 years later he contacted me to see if I was still interested because his property was being subdivided and the back block was being sold.
So as a buying approach it can work, but personalise it and appeal to the Owner's emotion.