I have 2 cats (sisters) and I think it's highly worthwhile to have two of them to keep each other company. I have heard a lot of people say it's harder to introduce males together, I have no experience on this, but have heard lots of people say it, so it might be worth a question to your vet. For sure both cats will need to be neutered, if they aren't already. Helpful hints:
Make the introductions SLOWLY! Keep new kitty confined somewhere where he/she can interact with resident kitty only under the door, for example, that way they can get used to each others' scents without having to be in contact with each other. You can then gradually increase the type of exposure, like exchanging beddings and putting new baby in a carrier and allowing sniffing etc. I'm sure if you do a google search you can find lots of good sites. Your vet can also provide you with good information, I'm sure. That's another important thing...you'll need to make sure the new one you're bringing in doesn't have anythig that can be passed on to resident kitty. You'll also have to consider that resident kitty no longer has claws while new kitty will.
My post is getting long, so I'll close with, I think 2 kitties is a GREAT idea if excercised with care and committment. Please do also be prepared for those rare extreme cases of cats REALLY not getting along. Those can require veterinary intervention with medication, and sometimes the best choice is re-homing the new addition. It's rare, I think, but I just want to make you aware of your options.
I hope that helps some.
here's my dynamic duo, lol.