That is a good question. Only the people paying for things should have a vote.
They'd find a way to get around that. I'd go with "anyone who's paying for it paying and can be trusted with a firearm."
Now, this is arguably going to deny people representation. Under the doctrine of "no taxation without representation" anyone who's being denied the right to keep and bear arms can choose whether they want to pay their taxes and get to vote, or not get to vote and not owe any taxes.