Wiggum House

Have you done all quests ?

https://forums.ea.com/en/the-simpsons-tapped-out/discussion/25099/the-complete-tapped-out-guide-walkthrough-updated-with-level-39-quests

A more up-to date thread here:
https://forums.ea.com/en/the-simpsons-tapped-out/discussion/90074/tips-for-new-players/p1
Building prices and build times from level 10. NOTE: You may not receive quest lines for buildings in the order listed.
Buildings in BLUE are for squidport, RED are for Krustyland, YELLOW do not have a task to build them and GREEN require Springfield Heights materials.
Quests for buildings will not unlock until prerequisite quest lines have been completed. Event related quests may take precedence over main quest lines. Levels shown are the minimum XP level ( game level ) required.
http://i.imgur.com/MScQZI2l.jpg
http://i.imgur.com/hlnhQYtl.jpg
Wiggum house is minimumlevel 26. Generally you have to build level items in order.

If you're level 31 you just need to complete the previous characters quest. They each unlock one by one as you do their quest.