Anyone living in a rented apartment knows that making major changes is only possible to a limited extent, or always requires permission from the landlord. It is of course still possible to put a shelf up on the wall and to paint the living room a different color, but the basic structure of the apartment must not be altered. In addition, any modifications you make, such as painting the walls, drilling holes or integrating cat flaps must be undone when you move out.
The situation is completely different if the property actually belongs to you: you are free to design everything in any way you like, providing you observe the applicable building regulations – and, in the case of condominiums, the regulations of the condominium owners’ association. This gives you long planning reliability because it is more difficult for either party to terminate the living arrangements.