For the cost of demo, call the City of Dayton Housing Inspection office. They can tell you the cost of demo.
For fixing up, it varies from house-to-house depending on condition.
Pick a couple of houses that you see.
Then use the worksheet that is linked herewith, fill in the appropriate blanks, and go to your local Home Depot or Lowe's and work up the costs of your materials. You may have to call a couple of contractors, too, if the house needs foundation work, roofing, or something else that requires someone with the know-how and equipment.