How do you all do rehab/renovation estimates?

[Zac Barnes]

So I'm very new to this and I'm just practicing analysis on some multi-family properties I come across with no intention to buy...yet ;). I find that most of the data (home value, potential rents, taxes) is easy to come by. The hardest part for me is trying to determine my repair/rehab costs. Some of these properties look like they need substantial renovations. My plan would be to go the BRRRR route.

How do you all do estimates for how much a potential repair would cost? Is there a book or some resource I can look into? Thanks upfront for any advice :)