Board Thread:General Discussion/@comment-16093571-20130825053428/@comment-24261859-20140118065802

Dark Brotherhood radiant quests after the main quest (which gets you 20,000 on its own, plus the jobs from Nazir) yield 1,000 gold per kill at a mid level. Of course, if you don't want to be an assassin, then this is not an option.

Dungeon crawls, get the loot at the end, smith it as far as you can and enchant it, then sell. Boom. Money. Looting Dwemer dungeons is especially lucrative if you can make Dwarven armor and weapons.