We've always had at least one dog. We've had two a few times, too. It depends on a lot of things. I agree with those who've mentioned doubling the cost and workload. If you have two dogs that get along well, you can have double the love. If you have two that don't, it can be double the angst and stress, so you have to choose wisely when you bring a second dog into the home. Dogs can be funny about territory and dominance and such, and problems may not always present themselves right away. There are a lot of dogs in shelters because they didn't get along with other dogs in the home. (And of course you always have to take into consideration what other, perhaps not so good experiences, a rescue dog brings into the home - and puppies may not be perfect, either.) So pay really close attention to how they act together, and if there are any red flags at all, don't try to "talk yourself into it". If it's possible to do a trial, that might be best. (I like the idea of fostering as well.)
I've been watching Petfinder for a long time, too. I go back and forth whether I want a second dog now. We pet-sat a few weeks ago and got a taste of what it would be like having another dog here that wanted to cuddle with us exclusively and not play with our dog. Not much fun for our dog at all, and although he liked this dog, it changed the dynamic in our household. And just last night our neighobor's dog came over for a while (with his person), so the dogs know eachother. My dog was ready to relax after being out all day and was happy to chill out. The other dog sat obsessively looking at him and wanted to jump on him every chance he got, I had to physically keep them apart. Now granted, maybe if they were either both tired or both energetic it would've been better. But I think there's more a dominance thing going on and it would be problematic if they lived together. This scares me with Petfinder when I think about adopting a dog from out of state or whatever - even though the dog may seem like a great dog, and in fact may be a great dog, I'd always want to see how any new dog got along in the house with my current dog before I brought another dog in to live with us. Hence the fostering may be a good thing for us, too.
I also agree with the pp who said a lot of it depends on your life stage, and I agree with this sentiment, too.
We also used to take our single dog lots of places with us (not to other people's homes, but to the park, the soccer field, etc.) When you've got two, it becomes more of a production and we haven't ended up taking both of them nearly as many places as we did when there was just one.
Right now we're able to take our dog a lot of places with us and I like that. Not sure I want to upset the apple cart. Also having two kids starting college next year brings up budgetary issues. I guess we'll see what happens and if the right dog comes along, it might be hard to resist.
So, re-looking at the OP, I'm bolding the potential red flags I see:
I need to put a website block on Petfinder so I stop falling in love with all the homeless animals. I have "dog fever" and keep mulling over adding a second dog to our family. I'd love to hear thoughts on the pros and cons of two dogs over one. Our current dog is small and loves other animals, so I don't worry about them not getting along, my main fear is the added expense. We also do not have a fenced yard, we walk the dog for all potty breaks, so that is a big consideration
We have a big fenced yard, so that part is easy for us. But there are a lot of considerations, really.
HTH, and good luck!