Voting, age 25.
Military service 25.
Homeownership 25.
Age of sexual consent/marriage 25.
Consumption of alcohol 25.
Gun ownership, etc.
However, I don't agree with the ages, but I do agree everything should be consistant. One thing that really chapped my butt is my soldiers, 17-20 couldn't drink, but had been on 2-3 tours in the 'stan and Iraq, nor could they purchase a handgun for defense when home on leave. I think the best answer is like Heinlein said: Compulsary military service, 3 years, THEN you get citizen rights contained in Consitution.
Can't hack it in the military? Good. Go build a something in the Middle East or Central Asia for 3 years surrounded by people trying to kill you for your beliefs. If you make it back, you are a citizen with all rights granted! (*and these little narcissistic kids today that only care about Idol, Xbox, selfies, twerking, Mylie Cyrus, and JustaBeiber will be alot more appreciative of the US).
[ I think the best answer is like Heinlein said: Compulsary military service, 3 years, THEN you get citizen rights contained in Consitution. ]
I agree, only veterans should vote.