How do I BRRR into a new property from an existing one?

[Shae Langley]

Hi.  I have a property in Atlanta, GA that has gone up in home equity value about $50k since I bought it a year ago.  I would like to invest into a second property with the equity via a home equity line of credit (not cash out refinance).  With that $50k, ideally I invest into a new property with $30k down payment, and then saving $20k for renovations (or maybe all towards a down payment, flexible with where the money goes).  With that being said, I'm a bit confused on the loan/backend side of all of this....a few questions below :

-Can the ARV be determined before the repairs are done / during the offer/inspection process via a contractor? Or would a loan agent need to quote the ARV? Is this ARV guaranteed? Is it a guesstimate and can only really be determined post renovations?

-Should I take out more than $50k from my original property? What is a good rule of thumb for the amount you can/should with-drawl?   

Thank you!