In the early days of the Republic, one had to be at least a landowner to vote.
I believe in the spirit of that requirement, which is that a voter should have some skin in the game and be a productive citizen. In the early days, ownership of land was basically a guarantee of that. It no longer is.
I do believe that there should be some similar requirement, more relevant in the 21st century. Until we abolish the IRS and go to a consumption tax, I think paying taxes would be a pretty good option. Anyone who gets out more than he puts in does not vote. This prevents the takers from voting themselves more money from they payers.