I have used a signature line of credit from keybank to purchase and flip property. My wife and I have very good credit and assets, so I am sure that helped on our application. I also had a few years of paying on a Line of Equity (LOE - 100K) on my primary residence prior to applying for the signature line (30K).
Banks will Normally go up to about 85% Loan to value LTV for the 1st mortgage and LOE combine. Signature line just depends on your income and credit history. Having a banking relationship always helps.
I used mine just for cash purchase, then paid them off in full when the project was complete.