I'm a single guy living alone and I have a Puggle, half Pug and half Beagle. She's a nice size, about 24 lbs and was easy to train and I can leave her for 9 hours with no accidents. She's the most affectionate dog that I ever had, loves to snuggle, loves her daily walks, loves car rides and is great with kids and other dogs.
You need to find one that will fit your life style. If you are athletic then you should get a high energy breed. If you are gone for most of the day you need to get a laid back one that can handle being alone. Do a search for quizzes that match you with a breed. There are several out there. Then please go to a shelter or rescue and get one. If you get one that is a little bit older you could get one that is already housebroken. That is always a bonus!
If you go through a computer site like PetFinder, you can find adoptable dogs that already have their shots and are neutered. The descriptions will also tell you if the dog is already housebroken, which many of them are.
Okay, I just have to say this first. Do not get a little dog. They are so irritable with their constant yapping and they wont do as they are told. Not exactly very smart either. Your best of getting a large docile breed like a lab or golden retriever. I myself have 2 German shepherds. They are very intelligent loyal and lovable dogs. Huskies are a good breed too, great companion dogs. If you are a active person a kelpie or border collie are energetic dogs. Best if you do some research on dog breeds and see which one suits you.