There's no one-size-fits-all answer to this question. Rules and regulations and guidelines relating to insurance will:
FYI: many countries offering working holiday visas (WHVs) will insist that a minimum level of insurance (medical, travel, etc.) is maintained by the visitor for the duration of their stay.
Therefore if you're a local host, you should review both the insurance policies of the person(s) you're planning to host, and you may find that your home and contents insurance provides you with additional coverage, e.g. from theft, injury, etc.
If in doubt, please speak with an insurance professional about your specific circumstances.
See also our Terms & Conditions: https://www.adoptabackpacker.com/terms-conditions