The Krabappel Apartment in The Simpsons: Tapped Out is a building released dedicated to the High School teacher at Springfield Elementary, Edna Krabappel.
This building becomes available at level 22 but with the release of the new updates, you are released to complete any pending quests to unlock the building after you have reached level 22. If you have not been following your quests, your screen icon will change from Level 22 to “Quest” when you do reach the level.
After unlocking the apartment, you can purchase the apartment for 162,000 cash in your Tapped Out game. Doing so will unlock Edna Krabappel into your Tapped Out city along with her quests and interaction with other characters.