No one should be voting who is not self-supporting.
So, that would mean no one below the age of consent, and for that matter, no one who is below the usual college age.
Based on that, 22 minimum. By that time you’re typically out of college, out of your first term in the military, and out of your parents home (at least for the first time...)
Hell....no...21 should be minimum voting age and even that’s a stretch....a voter needs to have some life experience before making such decisions of consequence...