It is important to keep in mind that great risk exposure does not automatically guarantee greater rewards.
One rule of thumb to keep in mind is that any monies for short-term goals such as this home purchase should not be invested in the stock market. Market volatility could present problems if you do not have a longer time horizon for such investments.
The key to keep in mind with IRAs is you're taking a long-term horizon. You've got to go in thinking there's going to be ups and there's going to be downs.