UK's vacant tax seems sensible:
Council Tax on Empty Properties (UK):
- Properties that are empty for two years or more may be subjected to an "empty homes premium" that significantly increases the Council Tax charge. As of now, this premium can be:
- 100% extra for homes empty for at least two years,
- 200% for those empty for five years or more, and
- 300% for properties empty for ten years or more.
- Impacts: These policies are part of broader efforts to mitigate the effects of property vacancy on communities, reduce housing shortages, and ensure optimal use of housing stock. Councils have significant autonomy in determining the rate of discount or premium applied, making the tax impact highly localized.
https://www.gov.uk/council-tax/secon...%20your%20work
Canada and Australia's regimes are also worth considering.
https://www.letsgethome.com/en/blog/...a-australia-88
Hong Kong can start with retail and commerical units first.