A door last the life of the house. Doors do not fall off before the end of the life of the house. Charge the tenant $2500 and give him the old doors. Whatever he can get for the doors is what the prorate should be. If the doors are not any good to him, they are not any good to you either. You may want to think about looking around for a good set of used doors. Then there would be no prorate. Because you will not be getting new doors. Do not forget that there will be some labor involved too.