Hi Fred, according to Turkish Civil Code, your grandma needs to be kept under guardianship. As a rule, the guardianship is a public duty however private guardianship is available in some circumstances. Considering your case, since your grandma has properties in rent which can be deemed as a "business", a private guardianship can be granted to "family council" to be established. Family council consists of 3 members who should be "close relatives." Coming back to the case, the guardianship for the reason of "mental illness or mental defect" can ONLY be granted upon a test report from a hospital. No other way, unfortunately. Nevertheless, if you claim a guardianship for the reason of "bad management of the goods/properties", you will not need a test report; but in this case, the court will hear the person who shall be kept under guardianship, namely your grandma.
Please do not hesitate to ask any question if any part of my explaination is vague.

All the best,

Ahmet Sirvan KILIC
Attorney at Law
Istanbul Bar