Schwab US Broad Market ETF (SCHB) has a nice 0.03% expense ratio. But it has less than half the funds of the Vanguard Total Stock Market since it tracks the S&P 1500 index (the S&P 500 being the famous large cap part).
When you pick between "Total Bond Market" and "Short Term Bond" funds, take a look at yield and duration. Yield tells you how much the fund pays you, and duration tells you the damage if interest rates go up. For example, Schwab Total Bond Market Fund has a 30-day SEC yield of 1.68% with a duration of 5.32 years. The expense ratio is a concern, though: the 0.29% is actually discounted from the actual 0.54% before discount.
If rates go up 0.33%, the fund roughly breaks even for the year (0.33 x 5.32 duration = -1.75% vs yield of 1.68%). But a fund that costs 0.54% to run, and needs to discount that down to 0.29% means they could let the expense ratio rise any year. Compare it to Vanguard Total Bond Market ETF (BND) at 0.06% and that's a lot of yield to give up on a bond fund.
I'd favor the Schwab US Broad Market ETF (SCHB) for the stock portion, and hope you can find the lowest cost bond index fund they have. Their Total Bond market ETF seems a little higher than average, but it probably won't be that significant given bonds are 10-20% of most starting portfolios - but my advice would be different for someone closer to retirement age, where bonds are near 50% of many retirement portfolios.
