If you aim to start kendo, it can not only be expensive but it will take a lot of blood, sweat and tears. Many people enter the sport thinking that they'll learn quickly and they'll be swinging a sword around like their favorite characters from movies or anime. It's a long-term sport. The gear can be expensive. The armor can cost $500+ USD, but it's something that will last for the rest of your life. Here in Japan they sometimes even hand it down to their children. It's pretty well-made!

Fencing is similar to kendo in regard to the amount of effort you must put into it. It's hard and tiring both mentally and physically. You learn a lot through it, just like kendo, about yourself, your heart, etc. But it isn't something that you will be able to master quickly. It's something people do long-term. I'm not sure how expensive the armor is for fencing, but I've heard it can be rather spendy.

I don't know much about boxing, but what I do know is that is more "in your face" so to speak. If you're not afraid of hitting someone or being hit without the protection of armor, perhaps this is your sport. Just like every other sport, you should probably do some research via youtube to find some real-life examples of what this sport is like.

As for my recommendation: I recommend kendo. I've been doing it for the past year and a half and I think it has become one of the best things about my life. It feels rewarding, I enjoy it, and it's a challenge. Whatever you do, make sure you like it! Many dojos (kendo training areas), gyms and fencing classes will usually let you watch or try once without paying a fee to see if you like it. :)

kendo

I think fencing is really cool!!

Their totally different things it depends on what you want to do