Wow this surprises me that it is happening, however the question comes down to the planning conditions imposed at the time of the almshouse development as to if this could happen / is permitted and the impact on any charity insurance.
My view is if the beneficiary is not using the drive for personal use and the planning permission / insurance impact don’t prevent this from happening, then this could be a useful way of the charity generating additional funds, perhaps where the beneficiary manages for the trustees and agrees an income share agreement, i.e. 75% to charity / 25% beneficiary, it would be a nightmare to manage and would rely on honesty