Offer your thoughts or opinion on the input financial query or topic using your financial background.

I'm 20 and starting to build up for my mortgage downpayment, where should I put my money for optimal growth?
Good job.  Assuming that you are also contributing to retirement, you are bound to be a wealthy person.  I'm not really sure how Australia works as far as retirement, but I am pretty sure you are taking care of that too.    Given your time frame (more than 5 years) I would consider investing at least a portion of the money.  If I was you, I would tend to make that amount significant, say 75% in mutual funds, 25% in your high interest savings.  The ratio you choose is up to you, but I would be heavier in the investment than savings side.  As the time for home purchase approaches, you may want more in savings and less in investments. You may want  to look at a mutual fund with a low beta.  Beta is a measure of the price volatility.  I did a google search on low beta funds, and came up with a number of good articles that explains this further.  Having a fund with a low beta insulates you, a bit, from radical swings in the market allowing you to count more on the money being there when needed. One way to get to the proper ratio, is to contribute all new money to the mutual fund until it is in proper balance.  This way you don't lower your interest rate for a month. Given your time frame, salary, and sense of responsibility you may be able to do the 100% down plan.  Again, good work!