HDB in Singapore means Housing Development Board. In Singapore, HDB is the public housing authority. HDB had built more than 1 million flats. The Housing and Development Act states that a person who purchased a leasehold interest from HDB is an owner of the flat. Buyers of HDB flats are lessees but under the Housing and Development Act, lessees are owners of the flats. As there are over 1 million HDB owners, they must be fully aware of the consequences of harbouring immigration offenders. It is an offence to habour immigration offenders such as illegal immigrants and overstayers. The HDB flats are meant for owner-occupation and owners are not allowed to sublet the whole flat without prior written permission from HDB. If you have HDB's approval to sublet and the tenant is a foreigner, the owners have to check the legal status of the foreigner who is going to be the tenant. You have to satisfy the due diligence test. If you have satisfied the due diligence test, you will not be prosecuted under the Immigration Act.