What will Singapore do if it commits the crime of harboring illegal aliens? And the owner doesn't know that he is illegal.

Accommodating illegal immigrants is more serious than illegal immigrants themselves, and the lightest punishment must be a fine.

If you know that the tenant is an illegal immigrant and provide him with housing, and the tenant is also engaged in other illegal activities (such as illegal work), you may even take away your unit in serious cases.

Besides, it's hard for you to prove that you don't know. Checking the tenant's certificate is a necessary step before renting a house. According to the regulations, you must submit the tenant's license information to HDB. So, either you rent it illegally without an inspection permit, or you rent it to illegal immigrants on purpose. Whoever does these two things will be fined, and the heaviest punishment is to recover the unit.

If you have any questions, ask them.