From the May 16 Straits Times:
“I LIVE in an HDB flat and I plan to set up a small business at home providing accounting services.
What do I need to do to get started?
What are some of the rules governing businesses based in HDB flats?
You will need to register your business with the Accounting Corporate and Regulatory Authority (Acra) and apply for the Home Office Scheme with the Housing Board (HDB).
Both registrations can be done on the Internet via the Online Business Licensing Service at the EnterpriseOne website http://business.gov.sg/licences
You may wish to note that you can have a maximum of only two non-residents working from your home office and that certain businesses are not allowed under this scheme.
For more details on the policies of this scheme, please visit http://www.hdb.gov.sg”