Estimate Repairs On Roof

[Victor Barboza]

I met up a motivated seller today. When he was in jail, several homeless people broke into the house and caught part of the roof on fire. The home is 1050 square feet. Only about half of the house's roof was caught on fire and made a hole of about 3 feet diameter around to the outside of the house. However, half of the roof does have fire damage. I will be getting a contractor. But, I wanted to get a little ahead and see what others thought. What do you estimate the cost would be to COMPLETELY repair the roof? 
Details: Built 1947, ARV 210K, 1050 Sqft.

I know it's best to get a contractor to get an exact estimate. But, what should be the highest I should be expecting to pay on this? And what could be just and average for such a repair? Thank you!