How to take care of a small dog in a small apartment?

It's not a case of adapting to dog to cat company, they were there first. And as yet, are your only responsibility. What are they like with dogs? If you know they would be too stressed and not adjust to the situation, it would be selfish to add a dog to the mix. Your responsibility lies first with the cats you already have.

As for potty training, don't use those pee pads. That teaches the dog to pee indoors, and it will end up just going anywhere it wants. However, house training without a garden can be done. I've done it. It just takes more patience and effort on your part. It's the same method as for people with gardens, just having to take the dog outside whenever it needs to go.

Having said that, since you live in a small apartment, is it a wise idea to get the dog at all? It's small, and you already have 2 people and 2 cats. People can't have a dog "just because they want one". That's why there are so many BYB's, shelters, and dogs being put to sleep. People acting on impulse, selfishly, without thinking it through

If the dog if puppy then it will be no problems about dog-cat thing. Cats might be jealous at the beginning but it will pass. Just introduce them nicely, be calm... First impressions are really important.

I suggest to google about meeting your dog 1st time, what you should do, what not...

About potty train... If he is a puppy he won't have everything in control when it comes to potty, so expect a lot of random 'pools' in your apartment. If you want to train him to go outside or in bathroom you just need a lot of rewards.

Tips: Never yell at him for doing it on wrong places, don't let him see you collecting his poop after he did on the wrong place, try to take him in to the bathroom every time you think it is about time and wait...

Buy some snacks for dogs and then every time he do 'those things' on the right spot say "Good dog" or whatever and give him one.. by the time, when he get used to it, he will scratch the door. Also when he learns where is spot for him then stop giving treats every time...and finally you can stop.

When he gets older, he will appreciate doing 'things' outside, because of the instincts or whatever, so it will be nice to walk him 2-3 times a day! (dogs live for those things, thrust me)

taking care of a small dog in a small apartment is exactly the same as taking care of any dog anywhere ... the problem here is a couple where both do not agree on the pet ... if you are already bitter the dog is coming, it does not bode well for the dog or the relationship ... guaranteed that dog is going to give your girlfriend unconditional love (you do not do that whether you think you do or not, if you loved her unconditionally you would want her to be happy and therefore facilitate her getting the puppy she wants) ... your girlfriend will chose you over the dog if it comes to that ... and how to housebreak a puppy, you take it outside often and do not leave the dog unsupervised ever in the apartment until it is housebroken ... no pee pads ever !!! the cats will be hit or miss ... especially with siamese ... they can be vicious little bastards and i would worry for a small puppy if by chance the cats decide they hate the puppy ... one swat with a claw to the pup's eye and you are looking at significant vet bills to fix that dog's eye ... the size of the shelter is not the point, it is the care the pets receive in that shelter ... i lived in a 550 square foot apartment with my boyfriend, my two dogs, and his two cats ... guess what broke us up, him wanting me to get rid of one of my dogs ...