Single individuals with adjusted gross incomes (AGI) under $120,000 can contribute the maximum amount to a Roth IRA, as can married individuals filing jointly with AGI under $189,000. You can contribute a reduced amount if you are single and have AGI between $120,000 and $135,000 or are married filing jointly with AGI between $189,000 and $199,000. This means, assuming a 3% inflation rate, parents will have to fork over almost half a million dollars in 18 years for a newborn's four-year education at an elite private college.