Buying and Selling: Buying or Selling a Rented Property
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2106
There is no problem in buying or selling a property that has been rented to someone else. However, the use of the property during the rental period belongs to the tenant/hiree (mustaʾjir). If the buyer does not know that the property has been given on rent or he bought the property supposing that the rental period is short, he can annul his transaction after discovering the situation.
-Ayatullah Sistani, Practical Laws of Islam, Buying and Selling