When the sisters entered religious life they took three vows, the vow of poverty, chastity and obedience.
A vow is a solemn promise that one makes to God. These are solemn promises that are not made lightly that where you can hold your hands behind your back and cross your fingers. These are not the false promises of the Pharisees where if you swore by the Temple or the altar you were not obligated. These are promises that need to be fulfilled. The most famous of the promises is chastity, and while it is important it is not the first. The first is poverty. By the vow of poverty the religious gives up all right to the disposal of whatever goods they happen to possess.
For example, if you were to give $20 to a priest of the Society of St Pius X and say, "Go have a good time with this Father." He could go to the mass or to a restaurant etc... (The SSPX don't take a vow of poverty) On the other hand if you give this same $20 ti a religious sister and say, "Go have a good time with this sister." She would have to bring that money back to the convent and it would be the mother superior who decides how the $20 would be spent. The property really doesn't belong to them it in the sense that they really own it. It is only given in trust, but it is their superiors who can decide ultimately what actually happens to it.