Great thing about Seattle is that we have several dog parks scattered all around the city. These are great places for you to take your dog and have it become socialized, but also for you to have an opportunity to expand your friend base and network with other local dog owners.
I personally have a service dog that lives in an apartment. My pluses, I also have a son, a cat, and a husband that all pick on her and play with her all the time. On the days that I'm up to it, I take her to the dog park to go play with her friends, and get some of that built up excess energy out of her. For the most part it's satisfying to her. There are days that I notice she's a little bored and that's when I switch things up a little and have either the son or hubby take her out so she can go play rough, or see other kids and have her licking fest.
I also have several toys that we play with all the time. That is another suggestion for you as well. Don't just stick with the normal tennis ball. Get some other things to give the dog a selection. Any toys that you decide to get, rope toys, tennis ball type toys, kongs, tug of war type toys, doesn't really matter which one, you always, and I do mean always have to keep an eye on them when they're playing with themselves. Some dogs can get to the point of boredom that even if you have taught them to only chew on those toys, they can still attempt to destroy them out of shear boredom. I have about 20 different toys for mine, and she has her own little shelf where we put them that she is allowed to go to and choose what toy she wants. Thru the day, they all eventually come out, but she loves the fact that when we tell her to get a toy, she gets to choose which one we tease her with.
Another thing you need to think about that not many do is the dog food. Most dogs don't do well with diet changes. Once you have a food that you start buying, you need to stay with that food. If you have to change for what ever reason, you need to do so slowly so you allow the dogs digestion to cope with the changes. What this means is that you mix the two foods together slowly bringing it to the point that the new food is the dominate and then the only one left. The other thing you want to think about too is where you store your food. Once you have dog food in your home (I have to buy those super large Costco bags), you want to limit the amount of bugs or rodents that see it as an invitation to come and invade you. The way I get around this is once I buy the food, I store it all in zip lock bags. One, this keeps the food fresh, which your dog will love you for...you don't want to eat stale chips do you? two, bugs won't be able to get into it as easy or rodents as you're getting rid of the food 'left out on the counter' bit. three...makes for easier clean up. Never ever ever feed a dog bones of any kind. I have personally worked in a Vet office and have seen the aftermath of shreaded intestinal tracks from bone consumption. Also, get in the habbit of not feeding people food..goes along the lines of don't change the diet.
Once you get into these type of habits it will make your life immensly easier for both of you. Establish a potty schedule and keep to it. You now officially have a little child with the mentality of a 5 year old living with you. You need to child proof your home. Not only do you need to get things out of reach of the deadly tail wag so it doesn't come barging thru and destroys everything in reach, but you also need to keep your garbage can lid on at all times. Dogs are curious creatures, and anything that smells good or looks good to them, they will do what ever they can in their power to get to it.
A book I would like to suggest to you to read is Marley and Me by Jeff Crogan (I think that's the spelling of the last name). This will show you worst case scenerio's. Owning a dog though is the most wonderful experience someone can have. You will have a loyal friend for life. There will be several sacrifices on your part as well. But they truely are worth it.
Bottom line is these 4 things, are you willing to dog proof your home, are you willing to keep a dog on a consistant diet regardless of cost, are you willing to set a consistant schedule for potty breaks, are you wiling take the dog out to play, outside and inside? I the answer to these is yes, then you're well on your way to becoming a dog owner. Just study the breeds to see which would be the best fit for you, and welcome to the new stage of your life. Oh, and congrats on your decision as well.