Re: Greetings from Omaha,NE
If you don't have a garage why not a big, big chain and padlock? Run it through the frame and wheels then lock it to something immovable like a balcony railing or sign post.
Master Lock has a bicycle lock that looks like a set of old leg irons. It uses a chain that looks like bike chain but is about two inches thick. This lock is pricy but supposed to be secure.
Some guys have built a bicycle sized shed to house their bikes but you'd need approval of the apartment owner/manager for that. Good luck.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"