It should be just like share holders. You get one vote for every $100 dollars you pay in federal tax. Want more votes? Pay more taxes. Don't pay taxes? You don't get to spend my tax money. Why should people who have little or no money invested get a say in how that money is to be spent?
I have what some would probably consider a radical theory on voting. I say kids ARE entitled to a vote, but until they are legal age it should be their parents casting the votes in their interest. After all, they are concerned for insuring the country's future for those who will inherit it. If the parents are not together, then only one can claim the vote(s) of the child(ren), kinda like with filing taxes.
Of course, I also think a voter should be required to take an IQ test to qualify to vote, or at least be able to pass a test covering some fundamentals of American history and government. My opinion is that if someone is ignorant of our history and government, then they are unlikely to be competent enough to make judgements concerning the well-being of the country.