Trouble with calculating rehab cost and ARV

[Jesus Garcia]

I am currently analyzing a lead to wholesale in the Bronx, NY using calculators provided by BP. I am having an issue calculating what the rehab cost would be without having a contractor visit the property. Any suggestions or is there no way in obtaining such number without having an inspection completed? Please advise. 

Also, to calculate ARV I used comps from property shark for properties that sold in September with similar sqft., bedrooms, and bathrooms to take an average of what they sold for. Is that a good approach?

Many thanks!