I had/have these SAME thoughts! For now... I've decided my lifestyle works better with one dog for now. I know he would love a playmate because we often spend a night or two a week at my dads house with their two dogs, and he's just sooo much happier and full of life. And he lived with my moms dog until she passed (he was around 10 months old, I think, when she died). I *almost* even got a rehome and totally chickened out.
http://www.yorkietalk.com/forums/gen...ould-i-do.html
I guess it just depends on your lifestyle. If Jackson never got any doggy interaction and he was home alone a lot, I would want a second more. But he gets to the dog park once or twice a week, gets to my dads house with fenced in yard and their dogs a few times a week, other relatives homes, he gets lots of attention and exercise every single day. I just decided, for now, it's so much easier with one. It's easier to put him in the car and go somewhere, I'm able to bring him to certain family members homes (for holidays and such, grandma's house, etc) and I really enjoy doing that; with 2 I just don't think it'd be possible. It's cheaper, I had to remember double the vet bills, double the food, double all the unnecessary collars, harnesses, and clothes I just "need" to buy!
My lifestyle accommodates one dog very nicely right now and I'm basically scared to change, or mess up a good thing.
I will get a second dog eventually. I know I will and I am planning on it. But I think I'm going to wait until my life changes a little bit. I think, if I owned my own home, if I were a little more financially stable, etc, I would definitely have a second dog.