I don’t know if I’m the best person to answer this question, but I wanted to put my two cents in anyway.
I live alone in a large(ish) apartment. It’s probably about the size of your living area. I fell madly in love with a pup that my dad bred from his hunting dog, a Labrador retriever. I loved his dog so much that I knew I wanted one of her puppies anyway. So I went to ridiculous lengths to fly a dog from Illinois to Boston so that I could have my little Angus.
Well, little Angus is now around 60 pounds at about 9 months old. And growing. And my advice to you may not be as completely logical and sensible as someone else’s.
If you love the animal, and you’re willing to go through the hassles involved in keeping him/her, then go for it. Seriously. I think the biggest problems pet owners face is that they are simply unwilling to do some things for their pets.
If you have family close by who can help out on occasion, if you have the time and energy, if you love dogs, then what are you waiting for! Please remember what no one else will tell you: Dogs exercise outside. The space they need in your home is only enough to eat and sleep. Sure, it’s easier to have a big dog in a bigger space, because you’re not so crowded…the dog’s less likely to knock over furniture, etc. But it’s not like you’re getting a great dane in a studio space!
One thing you might consider, is your financial situation. Will it be a big deal if you have to pay to keep the dog in a kennel for a weekend? What if you need to pay someone to walk him a couple times a week? I’m really lucky that my financial situation allows me to accommodate my lifestyle and have my pet. Frankly, it sounds like your lifestyle is quite compatible with a doggie.
Also, it’s GREAT of you to consider adopting an adult dog. I’ve done that before too…I got a five-year-old Siberian Husky from the humane society. She was housebroken, fairly obedient, and calmer than a puppy. This is a GREAT idea. Not only that, but it’s very kind because most people want puppies and it’s more difficult for shelters to find homes for full grown dogs. Think of it as giving the dog an option: Your home or the shelter. My sweet husky died and I still miss her, even though I have this big pup!
Some breeds are more “re-trainable” or adjust easily to a new situation. I know from research that it’s pretty easy to take in a Lab after they’ve lived with someone else. I don’t know how Boxers are on that score, but you could do some reading and find out. That way you’d know what kind of risk you were taking regarding handling of a previously mistreated animal. Sometimes those animals are so grateful that someone is nice to them that they’re extra sweet. That’s how my husky was!