Refinancing clarification BRRRR

[Dale Graham]

I just need clarification if anyone can explain. David mentions in his book to get pre-approved before buying the home to see what it will go for when using the BRRRR method, but how is that helpful when you want to know what it will cost after the rehab? And if you get pre-approved before the rehab, the bank will give you the cost of the property before any construction is done.