Just my two cents. I have a very active, medium-size dog. When I got him I was living in a house with a huge yard, blocks from the dog park. We went every day and he ran his ass off..
Now I live in a motel (temporarily), lots of walks, off leash a few times a week. I'm more cramped than Scruffy is. He's adapted beautifully. He has a comfy place to sleep, he can still drive me nuts with fetch, gets lots of walks, meets lots of humans, all the things he needs to make him happy. Dogs adapt.
I wouldn't have a mal in an apt, though, they'll shed you to death. But a short coat dog without the insulating layer of fur that a mal has would likely do just fine. But I would agree, it makes future rentals difficult, if not impossible. The reason I am in a motel is that I can't find a place to rent that takes a 45 lb dog, never mind a dane or some such.