Estimating Rehab Cost and Understanding how to not over Renovate

Hey BP, 

I am currently in the process of obtaining my first investment property. It is a duplex. I have a few questions really pertaining this BRRRR project. One of the main ones, is how did you guys estimate rehab cost. I know I need to get itemized bids for the property and what needs to be done, but I want to understand typical cost for renovations. This being flooring, paints, bathroom remodel, kitchen remodel...etc. How have you guys navigated this? What additional resources or videos can I watch to gain a more clear understanding? I also know you don't want to overly renovate for the area, but how do you know when enough is enough? I have been looking at available pictures of sold homes or even rented properties in the area. Is this a good strategy?