How to get good at estimating rehab costs?

[Michael Johnson]

Hi,

I want to get good at estimating rehab construction costs using contractors so I can do a deal analysis to prior to making an offer on the property to determine what is my max allowable offer to have a successful flip or BRRRR.

How can I get really good at it? 
is there books of construction costs? 
Youtube videos?

Should I try to work part time aa ann estimator for a construction company in my spare time? 

How did you guys figure out how to run a deal analysis and know the rough prices for bathroom remodel, kitchen remodel, plumbing, electrical, roofing, drywall, paint, landscaping, etc. 

Thank you