You're awesome! My partner and I became "foster failures" with our tenth foster, Percy. It's such a beautiful and rewarding experience. The pros and cons people have outlined here are really great, and I don't have anything to add. However, I do have some tips for you should you decide to become a foster parent.
-Be honest. Of course, be honest on your application and all. That goes without saying. What I mean is that you should be honest
about what kind of dog you can bring into your home. Our first couple of fosters ended up being pretty traumatic for our two little chihuahuas because we, as excited as we were to help and be great foster parents, weren't completely realistic and upfront with ourselves and the rescue organization about the type of dog that you can have. We said, "we'll take any one that you need us to!" Fostering is SO great, but should it be at the expense of your family's wellbeing? After our first two fosters had been adopted, we approached the organization and said that we wanted to try fostering more mellow, older dogs so that our little chihuahuas wouldn't be exhausted from hiding under the couch, haha.
-Expect that the dogs will have issues that you'll most likely have to help them work through. When you approach the situation with the mentality that these dogs have just had the roughest of lives handed to them, it makes it so much easier to see the world through their eyes. Opening yourself to what the dog really needs though can make the bonding experience so much better.
-Make a promise that you won't adopt your first foster dog, and take tissues to adoption day. Fostering is such a hard, thankless job. We get these dogs at a time in their lives when they have no other place to go. In so many cases, we're their saviors from a really cruel world. We help these dogs resolve their issues and teach them how fulfilling the bond between human and dog can be. Let me tell you, it can be pretty difficult to be happy for them when they're adopted and taken away from you. I cried in the car on the way home after several of our goldens got adopted. I promise though, it does get easier. The sense of pride you have for these dogs who are clearly going to have MUCH better lives than they ever expected is so worth it.
-Don't be scared to reach out to your foster parent peers for help - emotionally and otherwise. When I was fostering, I developed some really great relationships that started with a call to ask about training problems or just how to cope with losing my last foster.
-Monitor closely your own dogs reactions throughout the process. It can be traumatic for them - maybe even more so than for us. They have to adjust to a new dog, get to know (and maybe even love) the other dog, and then cope (or grieve) the loss of the newfound friend. I loved fostering, but I was fully prepared to stop the moment I felt like I was hurting them in any way.
I hope this helped. These are just things that were told to me when I was fostering by my mentors, and they aren't generally covered in the fostering handbook you'll read.
Best of luck!