There are no income limits for traditional IRAS1, however, there are income limits for tax-deductible contributions. You can contribute to a traditional IRA regardless of how much money you earn. However, you don't qualify to open a Roth IRA or to contribute to it if you earn too much money. If you don't have taxable compensation, but you file a joint return with a spouse who earns income, you can open an IRA in your name and make contributions through a spousal IRA.
A spousal IRA is an open IRA for a spouse who has no income of their own from work, usually from providing unpaid labor to their household. If you make too much money, you may still be able to contribute to a Roth IRA through a strategy called a clandestine Roth IRA. Yes, a person under 18 can contribute to a Roth IRA or a traditional IRA as long as they meet work income requirements and don't earn above the income limits. However, you can still contribute to a Roth IRA and make cumulative contributions to a Roth or traditional IRA regardless of your age.