What is the ruling regarding real estate properties that the father registered in his son's name, having contributed to their purchase and construction from the son's salary? Are these properties considered to be owned by the father? And what is the ruling on the son managing and developing these properties without receiving compensation for his effort and time?

If what the son paid to his father was a donation, then all properties belong to the father, and the son is not permitted to retract the donation, based on the Hadith (definition): "It is not lawful for a man to give a gift or bestow a donation and then retract it, except for a father in what he gives to his child." If it was in the form of a partnership, then the property registered to the son is his right. If what the father registered to the son exceeds his share, then the excess is a gift, and justice must be observed in it, unless the siblings consent.

It is obligatory to safeguard the wealth of the father who has lost his mental faculties, and it is not permissible to spend from it except for his own expenses and the expenses of those whose maintenance is obligatory upon him. This is because a guardian may not dispose of the ward's wealth except in a way that benefits the ward, and the guardian is liable for whatever he donates or spends extravagantly.

It is permissible for the son to take a fair wage (ujrat al-mithl) for developing his father's wealth if that requires time and effort.