Who says you don't need to apply for a business license to open a shop online? The law stipulates that all business activities must apply for a business license, otherwise it is unlicensed. As for those who rent the house to shops, engage in illegal business activities or use the house for other illegal activities, the landlord will bear joint and several liability for the crime. As for their debts, they belong to the scope of their business activities and have nothing to do with your house lease, so you are not liable for their debts. However, it is beneficial to suggest that your lease contract be written with the words: not used for illegal business activities and other illegal acts.