As soon as you have one perfect dog, you'll begin thinking how much fun he could have with a playmate. You're right! It really is no more work to have two or three than one - except of course, for the grooming. But before you add to your pet population, be sure your first dog is indeed well-trained. Then look around for another.
When you have one pet, it is easier if your second is not a tiny puppy so that you don't have to go through the paper-training stage while you have an adult, outdoor-trained dog in the house. In fact, a second dog a year old or more will probably suit everyone best.
Be sure your first dog is neutered (spayed or castrated) before introducing the newcomer. Likewise, have the new addition neutered before taking him home if possible. There is much less pack activity and aggression between neutered animals.
Let the dogs get acquainted on neutral territory: a park, building hallway, neighbor's yard, wherever. Once they seem relaxed together, take them into your home, but leave their leads on, dragging behind them. Be prepared for some rough play, running, jumping, and so on, and for housebreaking "accidents" resulting from excitement and exercise. Also be prepared for housebreaking "incidents" to establish territory and dominance. If things seem to get out of hand, just grab the leads and give a couple of hard jerks, yelling, "No!" If necessary, tie the dogs apart until they calm down. Let them sleep tied and start all over again under better control.
Be aware that the chasing and playing will calm down as the pets adjust to one another in a day or two. Just leave those leashes on when you're home, and put any limits on the play that seem necessary. When you go out, confine the dogs together, not separately. Obviously, leave them in an indestructible room to begin with. And, wonder of wonders: the smaller the room, the less the wilderness. So don't think two dogs need twice as much space as one. Hardly!
In all probability you'll see some status maneuvering between the pets. Keep out of it. You cannot change the dominance patterns inherent in their natures. It doesn't really matter who's on top-they'll work it out. You just relax and stop worrying about who has all the toys and who has none. That's life. But do get to work immediately with obedience training for your new dog, alternating training periods between the two of them. Soon they will sit and stay, down and stay, stand and stay together. Then they'll come together. And heel together. And you're home free.