Thanks for asking your question! I'm sorry to hear about your tax
issue and I'm going to try my best to help you understand or resolve it.
Thank you for your question, and thanks for using JustAnswer.com. Unfortunately the cost of razing the land is added to your son's basis in his land. It is not a depreciable cost.
According to Publication 551, "Demolition of building.
Add demolition costs and other losses incurred for the demolition of any building to the basis of the land on which the demolished building was located. Do not claim the costs as a current deduction
So, this is not depreciable. It is added to the basis of the land. Please let me know if you need anything additional. Thanks again for using JustAnswer.com and have a great day.
Publication 551 can be accessed HERE
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You should be aware that your question, as with most tax questions, can never really be answered completely...addressing all the permutations; that is because of the many assumptions that have to be made I have done my best to determine what I think you are asking and answering it in the most direct and understandable manner possible. If, however, after reviewing the questions, you have any uncertainties or further questions, please do not hesitate to ask.