Please consult with your sensei before purchasing any equipment for kendo or iaido. Most iaido sensei won't allow any of the knife-shop type swords in their dojo. They can recommend the proper length for you, along with other considerations. They may even not want you to buy a iaito right away, asking that you train with bokken to start.
For kendo or iaido equipment, many clubs have suppliers they like to deal with and have negotiated club discounts. So it's to your financial and technical advantage to consult with your sensei before any gear purchases.
Neil Gendzwill
Saskatoon Kendo Club