Yeah, I'm running into some difficulty on this front, since every smaller/apartment friendly breed I look at is high energy, and I really want a dog that is generally mellow and calm. I know it also depends on the individual though, so maybe I'll get lucky.
Basset Hound. Short enough that most apartments will accept them, and lazy enough that you won't need to run them everyday. A walk or two around the block and some playtime should be enough.
If you are willing to search a bit more for the right apartment you can get a larger dog and a Greyhound might be a good choice. They are usually couch potatos and perfectly happy to rest all day, but willing to go out if you want.
Training wise, they may not be the smartest cookies in the bunch, but I've rarely seen any serious problems with them. They can be great companions, and there are many groups dedicated to rescuing greyhounds from the track. Not good if you ever plan to have cats though.
Good luck in your search. I think it's great that you will adopt an older dog.