If you have narrowed down your list to one or two properties, consider chartering an aircraft to do a visual inspection. It might cost you $300-$500 but it allows additional validation of a significant investment. Even at 1,000 feet above ground level (AGL in pilot speak) you can quickly take some pictures, makes some notes, and assess things such as the terrain, trees or vegetation, and even a potential risk if say a neighbor has something on their property that could ultimately contaminate your water supply.
I know some readers will scream “my privacy!”. Here in the USA there is nothing illegal about what I’ve just suggested though – the FAA controls the airspace. – P.S.
HJL Comments: You can also consider a drone to perform the validation.