Again, if you wished to be supplied with money during a journey, or to pay a sum to any one at a distance, e.g.in Greece or Asia, your argentarius would arrange it for you by giving you letters of credit or bills of exchange on a banker at such towns as you might mention, and so save you the trouble of carrying a heavy weight of coin with you.

When, Cicero sent his son to the University of Athens, he wished to give him a generous allowance,--too generous, as we should think, for it amounted to about L640 a year,--and he asked Atticus whether it could be managed for him by _permutatio_, i.e.exchange, and received an affirmative answer[131].

So too when his beloved freedman secretary Tiro fell ill of fever at Patrae, Cicero finds it easy to get a local banker there to advance him all the money he needed, and to pay the doctor, engaging himself to repay the money to any agent whom the banker might name[132].
Your argentarius would also attend for you, or appoint an agent to attend, at any public auction in which you were interested as seller or purchaser, and would pay or receive the money for you,--a practice which must have greatly helped him in getting to know the current value of all kinds of property, and indeed in learning to understand human nature on its business side.

In the passage from the _pro Caecina_ quoted just now, a lady, Caesennia, wished to buy an estate; she employs an agent, Aebutius, no doubt recommended by her banker, and to him the estate is knocked down.

He undertakes that the argentarius of the vendor, who is present at the auction, shall be paid the value, and this is ultimately done by Caesennia, and the sum entered in the banker's books (tabulae).
But perhaps the most important part of the business was the finding money for those who were in want of it, i.e.making advances on interest.