My accounting advisor/teacher harped on more than one occasion about how good of an idea it is to put money away annually beginning when a person is in his twenties, so that by their sixties they can withdraw several hundred thousand dollars to have for their retirement years.

If you do the math, it really does sound like a good investment.  Put aside $3000-5000 a year for forty years or so and the money will be worth several times more than the total investment.

However:  
Luke 20:16-21
"And he spoke a similitude to them, saying: The land of a certain rich man brought forth plenty of fruits.  And he thought within himself, saying: What shall I do, because I have no room where to bestow my fruits? And he said: This will I do: I will pull down my barns, and will build greater; and into them will I gather all things that are grown to me, and my goods.  And I will say to my soul: Soul, thou hast much goods laid up for many years take thy rest; eat, drink, make good cheer. But God said to him: Thou fool, this night do they require thy soul of thee: and whose shall those things be which thou hast provided? So is he that layeth up treasure for himself, and is not rich towards God. And he said to his disciples: Therefore I say to you, be not solicitous for your life, what you shall eat; nor for your body, what you shall put on.

And:
Matthew 19:21-24
Jesus saith to him: If thou wilt be perfect, go sell what thou hast, and give to the poor, and thou shalt have treasure in heaven: and come follow me. And when the young man had heard this word, he went away sad: for he had great possessions. Then Jesus said to his disciples: Amen, I say to you, that a rich man shall hardly enter into the kingdom of heaven. And again I say to you: It is easier for a camel to pass through the eye of a needle, than for a rich man to enter into the kingdom of heaven.

There is the sin of usury, taking profit on the simple loan of money.

From Benedict XIV

You can read the rest here.

ON USURY AND OTHER DISHONEST PROFIT

I. The nature of the sin called usury has its proper place and origin in a loan contract. This financial contract between consenting parties demands, by its very nature, that one return to another only as much as he has received. The sin rests on the fact that sometimes the creditor desires more than he has given. Therefore he contends some gain is owed him beyond that which he loaned, but any gain which exceeds the amount he gave is illicit and usurious.

II. One cannot condone the sin of usury by arguing that the gain is not great or excessive, but rather moderate or small; neither can it be condoned by arguing that the borrower is rich; nor even by arguing that the money borrowed is not left idle, but is spent usefully, either to increase one's fortune, to purchase new estates, or to engage in business transactions. The law governing loans consists necessarily in the equality of what is given and returned; once the equality has been established, whoever demands more than that violates the terms of the loan. Therefore if one receives interest, he must make restitution according to the commutative bond of justice; its function in human contracts is to assure equality for each one. This law is to be observed in a holy manner. If not observed exactly, reparation must be made.

III. By these remarks, however, We do not deny that at times together with the loan contract certain other titles-which are not at all intrinsic to the contract-may run parallel with it. From these other titles, entirely just and legitimate reasons arise to demand something over and above the amount due on the contract. Nor is it denied that it is very often possible for someone, by means of contracts differing entirely from loans, to spend and invest money legitimately either to provide oneself with an annual income or to engage in legitimate trade and business. From these types of contracts honest gain may be made.

IV. There are many different contracts of this kind. In these contracts, if equality is not maintained, whatever is received over and above what is fair is a real injustice. Even though it may not fall under the precise rubric of usury (since all reciprocity, both open and hidden, is absent), restitution is obligated. Thus if everything is done correctly and weighed in the scales of justice, these same legitimate contracts suffice to provide a standard and a principle for engaging in commerce and fruitful business for the common good. Christian minds should not think that gainful commerce can flourish by usuries or other similar injustices. On the contrary We learn from divine Revelation that justice raises up nations; sin, however, makes nations miserable.

V. But you must diligently consider this, that some will falsely and rashly persuade themselves-and such people can be found anywhere-that together with loan contracts there are other legitimate titles or, excepting loan contracts, they might convince themselves that other just contracts exist, for which it is permissible to receive a moderate amount of interest. Should any one think like this, he will oppose not only the judgment of the Catholic Church on usury, but also common human sense and natural reason. Everyone knows that man is obliged in many instances to help his fellows with a simple, plain loan. Christ Himself teaches this: "Do not refuse to lend to him who asks you." In many circuмstances, no other true and just contract may be possible except for a loan. Whoever therefore wishes to follow his conscience must first diligently inquire if, along with the loan, another category exists by means of which the gain he seeks may be lawfully attained.

In the modern economic system nobody would lend money who wanted to obey Benedict 14th because of inflation and bankruptcy law.

Not saying he is wrong, but it is totally impractical to live like this.

How could you own a credit card or have a bank account without being part of the system of usury

Here is Fr. Watt's book on usury:

I'll really have to rethink my career decisions now.

I was thinking of applying to work for a local bank as a teller and work my way up, but if usury is sinful then it would probably be as bad as being a doctor prescribing birth control.

Exactly!