Re: Bokken, Jo, Sword?
If you are about regular size then a standard jo from say Tozando would do fine for the first many hours of practice in relation to aikido. If you are a strong mang buy a heavy one. I prefer around 2,5-2,7 cm in diameter.
I have heard sayings like "it should be the same length as the distance between the ground and your nipple (for a man)" or "it should go from the ground to your armpit". The best thing would probably be to use different sizes.
In my opinion the surface of the jo is very important. I don't like those that have been lackered. But they must be sanded down very nicely and they must be from a type of wood that dosen't splinter.
Regarding a sword.. well see my point of views in a different tread about a live sword. Don't get that... really.. don't.
We have as a rule that people train with bokken for a few years before I incourage them to buy an iaito. It might not be sharp, but it's still a piece of metal that could be really dangerous if you don't know what you do. Especially to those around you.. Apart from that I find Tozando.com make excellent Iaito. I am very happy about the balance and quality of mine.