Restrictions on size for BTO New ECs only accessible via JSS Mortgage Servicing Ratio (MSR) 1. Citizenship Singles can buy an HDB flat under the Single Singapore Citizen Scheme (SSCS) or Joint Singles Scheme (JSS). The latter allows up to four unrelated singles to co-own a flat. However, both schemes require you to be a Singapore citizen. 2. Age requirement To buy an HDB flat as a single, you have to be at least 35 years old (the other usual restrictions, such as ethnic quotas and being a Singaporean or Permanent Resident, also apply). If you’re unmarried or divorced, and have legal custody of a child, you and your child can form a family nucleus. This allows you to buy flats under the public scheme from the age of 21, subject to the usual eligibility requirements.