You can have as many cats as you want to have that you can properly care for and that local ordinances and any applicable property restrictions will legally allow.
To at least to some degree, we are left to figure this out for ourselves. What I will attempt here is to highlight issues you need to consider so that you can come to a decision that will be a good one for you and for your potential kitty companions.
This discussion will be based upon the assumption you plan to care for your kitties as indoor cats. This is a subject I offer more detail about in my blog post How To Keep Your Cat Out Of Trouble
How to Decide How Many Cats to Have
1. Are there laws where you live that limit the number of cats?
In the United States, I found wide variation state by state. You can check your state by entering into a search engine search field a phrase such as “number of cats”, followed by your state. Keep in mind there may be county or municipal laws that also apply, so be sure to check that as well.
Throughout the world there are laws that are different from country to country. Again, a search engine search should prove helpful.
2. Do you live in a rental home or apartment that limits how many cats?
This is a quite common restriction, particularly in apartments. You may have been given written rules and regulations when when you signed your lease.
If you do not have something in writing, ask for written permission from your landlord. You do not want to find yourself in a situation where a landlord gives verbal okay and then has a change of mind and you then have to make a decision about what to do about some of your pets in order to comply with your landlord’s demands.
A conflict with your landlord could put you in jeopardy of being evicted, so take care to make sure you are in compliance and have some legal recourse if there is a conflict.
3. Do you live where a home owners association limits how many cats?
The covenants of a Home Owners Association property typically covers this matter. If you own the condominium or home that you live in, you should have been given a copy when you signed the contract. If not, request one and review it to see what the rule is regarding pets.
If you are renting a home or condominium that is governed by a home owners association, both the covenants and your individual landlord should be consulted about how many cats you can have.
4. How much space do you have in your home?
I know this is obvious, but it is really important. Cats need stimulation. They are hunters, and when not sleeping they need an environment that allows them to act out their instincts. That includes room to roam, run, jump, and play.
Of course, a one-bedroom apartment will accommodate fewer kitties than a 5,000 square-foot house.
One other thing to keep in mind is that the more cats, the more litter boxes. Are you okay with perhaps having a litter box in your living room? I am okay with that, but I could understand why some folks might not be crazy about the idea.
I have a blog post 7 Tips to Choose a Litter Box that will show you an easy to clean litter box that will be easy for your cat to use.
5. Do you have the time and presence to provide care and companionship?
You need to be able to feed your cats on a schedule. They are animals of habit, and they know when it is breakfast or supper time.
You should make sure their litter boxes are kept clean. I cannot stress this strongly enough. Cats will go outside a litter box to avoid a soiled litter box.
A study reported on the National Library of Medicine website proposes that cats often do form a bond with humans, so spending time with your kitties is also very important. You need to be there for them.
6. Are there others in your household who are willing and able to help?
The important part of this question is whether or not anyone you are counting on to help you care for your cats is fully committed to the task. Someone who is half-hearted, or even reluctant, to feed cats and clean litter boxes is not going to create a happy situation for themselves, you, or your cats.
On the other hand, an enthusiastic lover of animals can be a great asset to you and your kitties. Of course, there will be the consideration of whether or not that person has the time to devote to the kitties.
7. Does your budget have room for the expenses you will incur?
These expenses include food, veterinary care, cat trees, scratching posts, cat beds, and toys. Cats need these things in order to have a quality of life that you want them to have.
You may have to consider whether it is best to have one cat that you can provide nice things for than to have several cats that may have to do without stuff they consider important.
P. S. My blog post Living With Your Cat may be a valuable resource for you if you wish to explore other aspects of being a cat caretaker.
Do Cats Get Along With Each Other?
There is no easy answer to this question because there is no one answer.
Cats tend to be territorial, but some express this in a home environment more than others. I have seen cats who considered their home to be their castle and their cat roommates their family. And you would be considered family too. They can be quite possessive about all this.
It is nevertheless still difficult to predict whether or not all the cats in a multiple cat household will get along with each other. Many times cats get along just fine, like the kitties in this photo:
The results of a study published in the journal PLoS ONE informs that cats are more likely to get along if they do not have elevated levels of testosterone and/or cortisol.
Since I presume your cats are neutered or spayed, high testosterone is probably not a problem.
Cortisol is a hormone produced by mammals experiencing stress. Therefore, I think we can deduce that the less stressful the cats’ environment, the more likely they will be okay with each other.
You can affect this situation by doing your best to create a happy home for your cats. For some help in accomplishing that, may I suggest my blog post How to Make Your Cat Happy.