 
		You can begin kendo practice in standard exercise clothing that is loose enough not to bind the shoulders; but, not loose enough to fall to the floor and get underfoot.
You should plan on purchasing a kendō keiko-gi {blouse} and kendō hakama {pants}  during your first quarter of study.  Kyu wear single weave, white keiko-gi; Dan wear 
single weave, blue or indigo keiko-gi.  Double or triple weaves gi 
are not recommended to wear in Arizona.
While sewn from a similar woven fabric, kendo and judō keiko-ki differ in the amount of re-inforced stiching across the front.  Kendō and aikidō hakama differ in the height of the koshiita: kendo higher, aikido lower.
While it is certainly acceptable to buy used clothing, care should be taken 
to purchase kendō correct items.