Well, I'm no bird expert...but as you know we have a GCC. Love him to pieces!!!
He has his own cage, but has supervised turn out time with our tiels. I have a huge cage that now houses our pigeon...but it came with the two tiels I rescued and at one time, thought that all our birds could live happily together with all that room.
Not the case...Franklin, although good most of the time, is quite a bully bird and I wouldn't trust him with another unsupervised.
Granted, every bird is his/her own personality...but if you do decide on another...you just might want a back up plan just incase your Con or your new GCC decided they aren't each other's cup of tea.
Also, as you know...we have 4 cockatiels...Chicken Little formed an extremely strong bond with our Charlie, so much so, that Chicken who is normally a very very sweet boy, becomes a vicious monster toward me when he's with Charlie. None the less, at times, I let the two of them hang out together. Never had a problem.
Yesterday, I had all the birds out, Chicken and Charlie are of course inseparable. I had to go back to work, put everyone away and decided to leave Chicken Little with Charlie happily snuggled up to each other and came home to find a HUGE amount of feathers in the bottom of Charlies cage. Both birds appeared fine...but what the heck???
When I got Chicken Little out to spend time with him and put him back in his own cage...to my shock...I found his back was nearly bald! His wings were covering his back where all his feathers had been plucked out.
Obviously in the 2 hours I was gone, there was a problem between them. So now, I won't be letting them stay together, unsupervised.
Our hens are housed together, and they get along great, so far, not a problem. You just never know...so I kindly advise you to have a back up plan incase your plan is kaboshed by your birds plan
Toni
So any advice on having multiple bird would be very appreciated! Thanks!
So without typing it all up again I just sum up what I was saying, I don't think it's wise to house birds together from the get go unless they were already bonded to each other from the beginning. It's kind of unreasonable to expect con to be okay with a newcomer invading his territory. It's not worth risking either of their lives or limbs. Is it a money issue or a space that makes you want to house them together? If it's a space issue, you could always get a cage that you can stack on top of the other one, although you really should quarantine the new bird first or at least get a vet check up to make sure he is healthy. If it's a money issue, check on craigslist, in my area there are always nice big cages online for $50-$100, and that's way less than you're going to spend on vet bills to recover from a bird fight.
I thought you were just going to bring him home and put him in cons cage(I have actually heard of people that try to do that). If you put him in a cage next to cons and allow them to interact under supervision, chances are eventually they will start to like each other. Although my conure and alexandrine are within eyesight of each other all the time and she still goes all godzilla on our little conure. :52: If it is seriously an issue of "if they can't stay in the same cage after x amount of time then you can't keep him", I don't think I would do it. If it's more along the lines of, you're room mate won't be happy about it but will deal with it, then that's a little different lol. Just be prepared if they don't ever hit it off, hopefully they will love each others company though. 
