Q: I am a federal employee and, yes, I invest the full amount possible in the Thrift Savings Plan. But I am looking at getting into a mutual fund. I am trying to find one that has an initial investment of $1,000 or less. Could you point me in the right direction? I have an account with Bank of America. -- R.S., Dallas

A: Most of the low-expense mutual funds have minimum initial deposits of $2,500 or more. Vanguard funds start at $3,000. Fidelity and T. Rowe Price funds start at $2,500. Funds with smaller initial deposits tend to have relatively high expense ratios.

One alternative is to open a brokerage account and buy exchange-traded funds. The Vanguard Total World Stock Index ETF (ticker: VT) has an expense ratio of 0.25 percent, the iShares S&P Target date 2020 ETF (ticker: TZG) has an expense ratio of 0.31 percent, and the iShares S&P 500 index ETF (ticker: IVV) has an expense ratio of 0.09 percent.

Now suppose you pay a commission of $13. That's a good deal lower than the $55 commission you'll pay on the purchase of a great many load funds that have $1,000 purchase minimums.

Better still: The longer your holding period, the lower your total cost. Hold IVV for 10 years, for instance, and your total cost of investment will average about 0.22 percent a year.

Q: Where can I get information on your Couch Potato investments? I know there are seven or eight different versions. Also, my wife and I are retired and in our 60s. Is a fixed annuity a bad choice for us? I am thinking about 15 percent to 20 percent of our total investments. -- J.M., by e-mail

A: Trailing time period performance figures for all the Couch Potato Building Block portfolios are posted monthly on my Web site, http://assetbuilder.com. You can get information on their construction by reading the columns in the Couch Potato investing section of the archive. You can also get a one-page "cookbook" in the Capital Gains section of the Web site.

Whether you are asking about an insurance contract that simply earns interest like a CD or a life annuity contract where you exchange a sum of money for the right to collect a monthly income for as long as you (and possibly your spouse) live, both have good uses in retirement portfolios. At times like the present, you may earn more interest in a CD-like annuity contract. A growing body of research suggests that having some lifetime income will increase the odds you'll never run out of money.

Q: I certainly agree with your recent column telling younger investors not to bail on stocks. However, I'm 80. I'm a Vanguard mutual fund investor. I moved from stock funds to money market and bond funds in early 2008. So I have lost only 5 percent or 10 percent to date -- not 45 percent. I understand that there is also risk with bonds, but less than stock. I don't have lots of years to rebuild.

My question: How should we older people preserve our principal? -- F.S., Mill Creek, Wash.

A: What you do at 80 depends very much on whether you have enough money to aspire to leaving some to kids or charities or whether you worry about running out of money before you run out of time. By the old rule of thumb -- that you should have your age in fixed-income -- anyone who is 80 should have no more than 20 percent in equities unless they have some assets clearly reserved as a future bequest.

We can quibble about that 20 percent figure, but it's a good starting point.

The older you are, the more important it is to guarantee that the cash you need will be available. That argues for a ladder of fixed-income securities such as bank CDs, Treasury obligations, or CD-like annuity contracts. Making a five-year ladder is a good start. You can also build a cashlike reserve fund by accumulating I Savings bonds. Sadly, how much you can accumulate will be limited by the $5,000 maximum annual purchase amount.