It depends. You can get an older puppy, that way they're still young and pretty "moldable," but they might already know some basic things, which makes it easier. Molly was somewhere around 7 or 8 months old when we got her, so she was still very much a puppy, but she was already housebroken and knew all the house rules (didn't jump up, didn't nip, etc.)
The puppy thing is tough. They're cute and fun and, depending on how training goes, it can be a really rewarding experience when they're older. But they will make you want to pull out your hair at times, lol. Adult dogs can have their issues too, but you'll probably know what they are before getting the dog, so you can decide if it's something you want to take on.