This sounds like a good idea, but the question is how can the property rights of these unmanaged houses be handed over to you? Another question is that in my country, such uninherited industries have to be collected. It belongs to the country, so it is better to consult the legal situation of your country before making a decision.
This can be done in a country like Tunisia because it is very corrupted and the guy who works in real estate office is willing to add a document stating that the owner sold his house to me in the past if I give him money, and he is taking the risk which is very low because we have no censorship/supervision at those corrupted administrations. So basically I will own the properties in a legal way and I will sell them to whoever interested to buy it cheap.
And no these uninherited houses do not belong to the government