You have to wait until your kid has earned income, and the max your kid can contribute is there earned income or the IRA max, whichever is lower.
But an IRA isn't the only way to help your kid save for the future. Here are some other options:
- 529 - no taxes on gains if used for education expenses, and some states offer tax incentives
- UTMA - basically a custodial account with tax advantages; the money will be in their name, so it could impact eligibility for financial aid
- trust fund - a lot more flexibility for the parent on when and how the child can use the funds
- Treasury bonds, like ibonds
I'm sure there are others.
Our plan is a 529 and an informal offer to match my kids' IRA contributions until the leave the house. We'll also offer to help in other ways, like a car for school (if needed), a down payment on a house (if wanted), etc. But aside from matching their IRA, we plan to retain control.