The hotel is about to close down. The employees work 20 days, have 10 days off, and are paid 20 days. Is this legal?

Illegal, rest hotels for non-workers must pay labor remuneration in accordance with the law.

For details, please refer to the Interim Provisions on Wage Payment:

Article 12 If the unit suspends work or production within a wage payment cycle not due to reasons caused by the workers, the employer shall comply with the provisions of the labor contract. Pay workers wages according to the standard. If the wage payment cycle exceeds one, if the worker provides normal labor, the labor remuneration paid to the worker shall not be lower than the local minimum wage standard; if the worker does not provide normal labor, it shall be handled in accordance with relevant national regulations.