When you decide to bring another cat home, do not forget about how your cat or cats will feel about a new cat. You may be a little more excited about getting a new cat than they will be letting another one in their territory. Even if your cat likes to be alone it could eventually accept or at least tolerate the new cat. You will also want to remember that cats can be very territorial, which is why you should always be careful when you introduce a new cat to the ones that you already have.
The length of time that it will take to get your cats to get along will depend on each cat’s temperament and personality. Each one will be different and should be treated accordingly. Do not forget about the cat or cats that you already have, they do not want to feel left out, so shower them with lots of love. Give each cat some quality time with you so they know that they are still appreciated and do not have to compete for your attention. Mine often will take turns with who gets to sit on mommy’s lap, but it took a while to get to that stage.
When bringing the new cat home, you will want to keep them in a separate room from the other cats for awhile. It will be so much easier in the long run that just having all of the cats together. It could prevent some fights between the cats. When you keep your new cat in a separate room, make sure they have plenty of food, water, toys, and a litter box.
Once you have the room set up for the new cat and they are comfortable, you will want to start bringing in things that have the scent of the other cat, and of course take something with their scent for the first cat. You can even try sharing one food dish for each cat, let one eat out of it and then take it for the other one.
Once both cats have gotten used to the scent, you can begin to feed them closer together. You can feed them close to the door where the new cat is staying and keep the door closed. Try feeding them at the same time this way. After a few times of feeding them this way should lessen or eliminate any hissing or growling. When they can eat and not hiss or growl at each other you can then introduce them to each other.
When they do finally meet face to face, there could still be some hissing and growling, but hopefully not too much. Your first cat still thinks that the house is their territory. Eventually they will get along; it could be a few days to over a year. It depends on the cats themselves. It took mine almost a year to finally at least tolerate each other.
There is one thing that brings all of my cats together no matter what their mood is or how much they do not want to be around the other cats. It is Playtime. All I have to do is get out the string and they all come running and grabbing and jumping for the feather or mouse on the end of the string. It is the most precious thing to see, all of them getting along and playing together.
So when you do decide to bring a new cat home, just be patient with all of them. They will eventually get along, or at least tolerate each other. Try getting them to play with each other; it may be what will bring them together.