Cash Loans - Renovation Costs

[Stefano Tavella]

Happy Monday! I'm new to the BRRRR Strategy and BiggerPockets so appreciate any help.

I'm trying to understand the Cash Loan/Hard-Money lender process for renovation costs. For the majority of the hard money lenders I've spoken to, they are willing to fund 100% of renovation costs as well as a percentage of the purchase price. 

My question pertains to determining the renovation budget. Is there any rule-of-thumb when calculating renovation costs? What happens if you don't use 100% of the renovation budget? Do you have any recommended hard-money lenders for a first-time buyer?