to get every building in TC you need to fulfill certain requirements. These requirements are:

Apartments: Unlocked in the tutorial.

Food Store: Unlocked in the tutorial.

City hall: Unlocked in the tutorial.

Apparel Shop: Have 2 Male Miis and 2 Female Miis, and solve 5 Problems.

Blessing Fountain: Have a Mii request the fountain be built when dealing with a Problem.

Mii News: Have 7 Miis total, and have at least 3 be male and 3 be female.

Job Diagnosis: Have 2 Male Miis, 2 Female Miis, and solve 15 Problems.

Compatibility Tester: 2 Male Miis, 2 Female Miis, solve 30 problems.

Pawn Shop: Have 5 Treasures.

Interior Shop: Have at least 20,000 Yen saved.

Question Hall: Have 4 total residents, and solve 60 problems.