I have three... and if you count the new puppy of my dd who lives with us..four.
I started with one, got a companion. My youngest dd had to have a dog, so I got one too.
She past, I got my dd's dog because she couldn't take care of him and then I decided I wanted a little girl and got the yorkie lol...my poor dh never knew what hit him. I live by the ask forgivness not permission rule
I think you should alway have more then one. They need companionship.
Why did I keep getting more? I just kept falling in love I guess.