Si. It's very sound advice, although you can usually start an account for much less than the stated minimum investment -- often as little as $0 -- if you sign up for autopayment to invest on a monthly basis.
Also, as Joan says, don't invest in a plain old individual account until you've maxed out your contribution to a retirement plan -- it creates HUGE tax benefits. If you're in the US and under about 50 years old, your best bet is almost certainly a roth IRA.
Also, see the thread on Managed Funds