Mr. Astor occupies an imposing mansion in Lafayette Place, and immediately adjoining is the magnificent library to which we have referred, and which should commemorate the name of the son as well as that of the father. At this house he spends that small portion of his time which is not occupied by his duties in Prince street, where he does a full day's work (Sundays excepted) every day in the week. Thus the daily routine of the richest man in America is a walk to and from home, of a half-mile or so, and close attention to business. The care of Mr. Astor's estate is a vast burden. His tenements of all grades number several hundreds, ranging from the dwelling at three hundred dollars per annum to the magnificent warehouse or hotel at thirty thousand dollars. To relieve himself from the more vexatious features of his business, he has committed his real estate collections to an agent who does the work well, and who is, no doubt, largely paid. He, with his clerks, collects rents, and makes returns of a rent-roll, whose very recital would be wearisome. As a matter of course, such a man must employ a small army of painters, carpenters, and other mechanics, in order to keep up suitable repairs. As Mr. Astor pays no insurance, the work of rebuilding after fires is in itself a large item. A large part of Mr. Astor's property consists of vacant lots, which are in continual demand, and which he generally prefers to hold rather than sell; hence he is much employed with architects and master-builders, and always has several blocks in course of erection. This is a very heavy burden, and were it not for the help derived from his family, would, we believe, crush him. However, his son, John Jacob, is quite a business man, and bears his share of the load. This young gentleman has shown his patriotism by serving in the army for the Union, in which he bears an important commission. In addition to this, Mr. Astor has the aid of a gentleman of business character and habits, once a member of one of the largest shipping houses in the city, who has become connected with the family by marriage. The labors of all these parties would not be more than adequate to the task of collecting interest on bonds, looking after dividends, etc., since that little fire-proof office in Prince street contains several millions of Government and State securities.