Q: I don't have lots of money to invest, and I can't commit a consistent amount of money to an "auto-invest" program. What's the best way for me to get started?

Until recently, commissions alone made it difficult to invest with little money. To get a diverse portfolio of stocks (at least 10), you would need to spend $100 or more in trading commissions, which is impractical if you only have a small amount to invest. Even buying a single ETF could be impractical without a lot of money. Additionally, mutual funds often have minimum investments of $1,000 or more.

Over the past few years, the concept of commission-free ETFs (exchange-traded funds) has really caught on. They're a great way for investors to get into stocks without a large commitment and without excessive fees.

Many of the leading brokers have ever-growing lists of commission-free ETFs to choose from. I use TD Ameritrade, and it offers more than 300 ETFs with no commissions. You can literally get a diversified stock investment for the cost of a single share. To name one example, the iShares Core Aggressive Allocation ETF (NYSEMKT:AOA) is designed as an all-in-one investment portfolio, with exposure to a wide variety of stocks and bonds. It has minimal ongoing fees and is available commission-free, and with a share price of about $54, that's all you would need to get started.

In a nutshell, if you don't have a ton of money to commit, I'd suggest finding a broker with a large selection of commission-free ETFs and buying a share or two whenever you can.