With a second mortgage you will have a fixed amount of money that is repayable over a fixed period of time or is due in full at a given time. A home equity line of credit, on the other hand, is much more open-ended. You have a line of credit that can be borrowed from as you wish, and generally has a variable rate as opposed to a fixed rate. Pay attention to the fact then when the APR is calculated it takes into account the interest rate charged plus points, finance charges and other fees, whereas with a home equity line the APR is calculated with solely the periodic interest rate.