Underwriting criteria vary from lender to lender. My suggestion would be for you to contact the lender or lenders you are using on the purchase of the properties to ask them what thier guidelines are. Be aware, I am seeing a nearly across the board tightening of 2nd loan and HELOCs for investment properties that make it increasingly difficult to access additional equity.
I have developed relationships with a number of lenders that provide investor, renovation and construction loans, feel free to click on my profile to contact me if you would like me to send this information to you. Good luck!