If a child is still a dependent of their parents (ie, a tax deduction for the parents, covered by parents health insurance, living in parents house are examples of dependency), they should have no vote. They are not functioning as an independent adult. Therefore, the minimum age to vote, 18, is fine, but some who are much older should not be eligible to vote for reasons of dependency.
-property owners
-net tax payers
-active duty service members and honorably discharged veterans.