Estimating rehab and rehab cost

[Wilson Lee]

Hey guys, 

  What are some great resources to teach a young person who's never had construction experience how to properly estimate rehab cost? 

  How do I know what needs upgraded or repaired? 

 How do I calculate material cost?  How do I figure out what materials are necessary for any given rehab? 

 How do I figure out the cost of labor? 

  I understand this is a broad topic but any resources would be appreciated.  Every rental property I own so far has not needed repairs but I'm wanting to get into some tougher rehab properties.