Owned under condominium ownership.
People often use the wordcondominiumas if it were a noun. Actually, it's a short form for the adjective "condominium ownership".
For example, the phrase "we have a condo", is a short form for "we have a condominium ownership apartment".
(The confusion probably arose because there are numerous apartments that are owned by condominium ownership. When people heard the word "condo" used in the same place as "apartment" or "apartment building", they probably assumed the two words were interchangeable.)