SpiffyEh - The advice for starting investing is different from the advice for saving for a down payment. The down payment is presumably needed soon - a few years from now. Retirement money can grow for decades, and shrug off most market corrections.
If you decide to invest the money you're saving for a down payment, be prepared to delay your purchase if the market corrects. Along those same lines, as you accumulate almost the amount you need, shift it to mostly bonds or cash. For example, you might risk 50/50 stocks and bonds with your down payment, but once you're 90% done you might shift to 90% bonds/cash. When you're ready to shop for a house, move it all into cash.
If you're sold on using Vanguard, then VTSAX (Vanguard Total Stock Market) is a good choice. Or rather, it's choosing everything instead of making a specific choice - the entire U.S. stock market. But as long as you're saving for a down payment and haven't saved enough, you want a lot of lower risk bonds (like Vanguard Total Bond Market).
You can also read up on the "3 fund portfolio" that uses of Total US stock, Total international stock, and Total bond market.