What is the meaning of 50 years in condominium?

Without a context or more information, the only answer can be 50 years is 50 years.

There are two meanings of the Word condominium as follows:

In Real Estate and Property Law: A condominium is defined as a building or complex in which units of property, such as apartments, are owned by individuals and common parts of the property, such as the grounds, common areas, facilities and building structure, are owned jointly by the unit owners.

In International Law: Joint sovereignty, especially joint rule of territory by two or more nations, or a plan to achieve it. This meaning is more of a concept than a reality and actual cases are rare.

Therefore, 50 years "in condominium" can mean the territory has been under joint sovereignty for 50 years. It can also mean a residential or commercial condominium project is 50 years old.