How to unlock homes for sale.
All you have to do is proceed through the story until you kill your first dragon outside of whiterun the king of the town will tell you he has told his steward to allow you to purchase land in his city after you tell him the dragon is dead. It costs 5000 gold "because being the dragon born and saving an entire city from destruction isn't worth anything." and uprages to the house will be close to 2000 gold total. Just keep progressing through the storyline and you will most likely unlock all of the other houses in due time.
Added by: Guest Nov 12th 2011, ID#7972