It appears that the 50 or so remaining residents in Youngstown’s abandoned neighborhoods are refusing to move, even with the offer of $50,000 payments.
I think that the obvious thing to do here is eminent domain. These green spaces are to be created for the benefit of the city, so as not to have to pay for utility service and police patrols to these areas.
Declare the green spaces a park, and take them to court. This is a legitimate public need.
Obviously, the use of eminent domain could be a political problem, so as an alternative, you could set up a special utility district in the neighborhoods intended for demolition.
When these folks get their bills to account for the real costs of their water, sewer, street lights, etc., they would likely leave.