So you want a katana.. you could buy a cheap replica, a iaido sword or a real sword. Replicas are crap don't waste a couple of bucks for a crappy, chinese-made wallhanger. Real swords cost far too much and have some problems, so settle for a iaido sword.
They are well-made, require no special care and can be used in practice. Buy one from this website,
Kendo, Iaido, Katana, Aikido and all other Budo Online Store - Tozando Online Shopping
You can get a nice sword for $300 or $500.
About the "problems" of real swords.. every real sword, after it's been drawn, has to be properly cleaned. It it isn't cleaned with a special powder, it will oxidate soon. What's more, real swords must be handled only by expert users, they're really dangerous, and since they're considered as weapons, in certain countries you have to get a permit before you get your sword.
I know two people who use real swords in iaido training. They paid their swords around $9000 and $5000.