To carry out these several different branches, it is of prime importance that the broker know his territory like a book. He must be an expert on values, both absolute and based on rentals. He naturally must be thoroughly familiar with prevailing rents; must know, at first hand, not a little about practical construction and repairs. Knowledge of mortgaging and financing also is important. He must be able to advise on matters of insurance - fire, liability, elevator, rental, plate-glass insurance. And, of course, he must be able to rent - to find tenants, to keep track for years of prospective occupants - and to hold tenants when he has good ones. This all implies tact and sound judgment, absolute system and the willingness to keep everlastingly at it. For owners - particularly those who inherit the property - rarely have the necessary unbiased point of view to manage their own buildings successfully.