Check the property on foot. Tramp around everywhere (with tick repellent on in Sussex County).
The property I looked at, 13 acres, is mostly wooded. I discovered three old trailers, several large piles of tires, and scores of large dumps of glass bottles and other miscellany.
I got prices from several sources for cleaning up the site and discovered it could not be done without cutting down many trees and putting in a bit of a road to make access possible to do the clean up.
All in all the cost ended up being about twenty percent of the price of the land and it was possible to negotiate the land price down to cover that cost. Well worth doing.
You never know what you will discover until you look close. Also check the recent sales in the immediate area for current actual prices per acre, to compare to asking price.