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I'm 20 and starting to build up for my mortgage downpayment, where should I put my money for optimal growth?
The big question is whether you will be flexible about when you'll get that house. The overall best investment (in terms of yielding a good risk/return ratio and requiring little effort) is a broad index fund (mutual or ETF), especially if you're contributing continuously and thereby take advantage of cost averaging. But the downside is that you have some volatility: during an economic downturn, your investment may be worth only half of what it's worth when the economy is booming. And of course it's very bad to have that happening just when you want to get your house. Then again, chances are that house prices will also go down in such times. If you want to avoid ever having to see the value of your investment go down, then you're pretty much stuck with things like your high-interest savings account (which sounds like a very good fit for your requirements.