The new owner will actually own the property in a legal way. The forge documents are done before the new owner buy the property, the guy who works in real estate office will add a document state that the owner sold his house to me in the past, and me as a new owner I will sell this property to an investor. and since these houses are neglected by their owners for decades and there was no trial to retrieve from descendants, it is really unlikely that they gonna wake up suddenly and ask about their properties and even if they do it is too late as it was done "legally" and there isn't much they can do.