What are the pros and cons of having two dogs?

I know lots of people with two dogs, and for a short time in the past I did too, but they didn’t always get along. I have one dog now, and it’s easier maybe to just have one, but would he want a dog friend? Maybe in the past the two that I had were just a bad match, because the other people I know with two or more don’t seem to have problems.

My dog is 7months old, neutered, and friendly but a little shy. I have a friend who is trying to find a home for a 3 month old male of the same breed (lab and border collie mix) and I don’t know if I should take him.