Is it permissible to reside in a building endowed to a charitable society while paying rent, given that the resident is the one who collects the rent?

If the questioner is the overseer (nazir) of the endowment (waqf), it is not permissible for him to lease it to himself, even for the fair market rent, due to the suspicion of favoritism. He is like an agent who cannot sell or lease to himself. However, if the questioner is merely an employee tasked with collecting rent from tenants, then there is no objection to him leasing the endowment from the overseer for the fair market rent, provided that this does not contradict the conditions set by the endower (waqif).