Depends on where you're at. I'd recommend contacting the dojos in your area. Check out the AUSKF site (http://www.auskf.info/main/schools.htm). At my dojo there is no "requirement," you just need to sign a waiver and we have kids under 10 practicing. It costs $8 a month plus $5 a year to the Hawaii Kendo Federation, and a one time $10 dojo initiation fee. This varies depending on the dojo. I've heard of other dojos here that charge $25 a month.
How "legally blind" are you? Can you see movement? If so, you may be at an early advantage over those who try to look at things . . . hehehe