Those 20 year events are certainly possible. And maybe we're due for a correction. Who knows?
The original question is really unanswerable. It is just not possible to beat inflation without some risk.
If the OPs friend wanted to minimize risk even more, he could keep some cash on the sidelines and invest it upon any drop to dollar cost average. Or he could incrementally move from equities to cash as his home buying event nears. But all of that is managing the assets, and not "parking" money somewhere. I think VTI is a close as we can get to the spirt of what was asked.
Or... it's the GT3 and a heated garage.
