Mortgage: The day you get the money, is the day to start to pay interest for whole thing. You have to take the money at once, no matter you use it now or use it few months later. You have to pay back every month. It is not flexible in the payment schedule. Good thing: variable mortgage has the lowest interest rate in all loans.
Home equity line of credit: You only pay interest for the money you spend, pay back money is flexible. The interests is little higher than mortgage.
Use line of credit as a backup for emergency use or purchase, as long as you know you will pay back in short period of time.
Use mortgage for house purchase or investment. The payment should be in your monthly budget