Why not?
As long as you have the time, money, and energy, I don't see why not.
Either sex should be fine. Getting a gurl may ease the transition. Depends on our boy's personality. You could have a meet and greet first.
We added a smal breed boy to our family after our girl was the lone dog for ten years. She does not love other dogs. It was rocky at first. She still terrorizes him, but it is pretty apparent that she really enjoys herself when doing this.
They like to play..on her terms only. If we had gotten a second small breed female I'm ot so sure it would have worked out.