How much to set aside for a new roof?

[Ricky Sabogal]

I am analyzing a fix and flip property in the Hampton Roads, Virginia area.  I went to see the property and while I think 80k renovations to turn this property around is reasonable, it needs a new roof.  In looking at the roof (I'm not a roofing expert) I know it will need new shingles, but there is also some wood rotting that I is visible from the outside, so I am hesitant that the frame under the shingles are also compromised.  While I know prices will vary by market, does anyone have any idea of how much extra I should plan for the possibility of a new frame?  Thanks for any and all input!