A recent report from Charles Schwab (SCHW, news) indicated that 67% of unmarried Americans are saving for retirement, compared with about 85% of married couples (across all age groups). Separately, a depressing report from PNC Financial Services (PNC, news) suggested that 18% of 20- to 29-year-olds "whose adult lives began amid the 2008 Great Recession" believe they will retire comfortably.

The surveys suggest that if you're young and single, you probably aren't thinking about retirement. And those who are probably don't bother to invest.

If this sounds like someone you know (or are related to), keep in mind that when it comes to retirement planning, a little goes a long way. Consider these three ways to retire with $1 million:

1. You invest $2,700 per year for 60 years, assuming an annual return of 5%.
2. You invest $14,500 per year for 30 years, assuming an annual return of 5%.
3. You invest $44,500 per year for 15 years, assuming an annual return of 5%.

The first scenario fits more comfortably in most family budgets, requiring a mere $225 a month. The total capital needed to generate that $1 million nest egg is a mere $162,000. For the second scenario, it is $435,000, and it's $667,500 for the third.

In short, compound interest on the proceeds from early investments puts money in your pocket while at the same time saving you money by lowering the outlays into your 401k or IRA. It's a win-win.

So where should today's young bachelors and bachelorettes invest their $225 monthly savings? Here are three investments to consider:

Vanguard Target Retirement 2050

Like other "target-date" retirement funds, Vanguard Target Retirement 2050 (VFIFX) is a good option for young investors because it automatically adjusts risk levels over time. So investors don't need to move money around on their own or perform exhaustive research.

The Target Retirement 2050 fund is perfect for 20-somethings with 40 years or more until retirement because it is aggressive at first and gradually becomes conservative as the retirement "target" of 2050 approaches.

The big downside, of course, is that if you plan on retiring early or late, this cookie-cutter approach might not suit you. You have to be comfortable with the "target" of this fund when you buy in, since that ultimate goal drives all the decisions.

Also, this investment vehicle is a "fund of funds," meaning it invests in mutual funds and not individual stocks or bonds. There is a risk of redundancy this way -- or a "too many cooks in the kitchen" approach -- because there are many managers for these disparate investments. Then again, if all those folks are doing a great job, it might be in your best interest to share in the success of a few different strategies.

The fund has a minimum buy-in of $1,000, which is the lowest in the business.

Schwab S&P 500 Index

If you are planning decades ahead, it's probably because you believe in the wealth-building power of the stock market. You have confidence that 40 or 50 years from now there will be a significantly higher value for most stocks -- and that picking individual winners is less important than just riding the rising tide.

But which so-called "index" fund should you buy? Fidelity has a number of great broad-market funds with low expenses, for example -- but a $10,000 minimum investment is required. Not exactly accessible to 20-somethings.

That's why Charles Schwab has a real winner with its Schwab S&P 500 Index (SWPPX) fund. The minimum buy-in for your initial purchase is $100. And with an expense ratio of a mere 0.09%, your investment will not be eroded by management fees, either.