To rightly understand the first proverb here in verse 15, we must push on to read it with the proverb in verse 16. If we do not do this, we will think that the acquisition of money is the end of man's existance. Although God encourages us to prepare for the future and to work hard so that through His blessing we may leave an inheritance to our children's children, this does not mean that gaining wealth is to be our highest aim.
We first learn of the fact that money can provide a measure of protection. The rich man's wealth is his fortress. There is much that a rich man can do to protect himself from harm due to his wealth. He is protected from much in life due to this. A fortress is a place one stays during an attack - it was a place of safety. For the rich man - his wealth can prevent him from a quick ruin by difficult circumstances. One example for us to remember is the wisdom of setting aside money for problems that we know will come in the future. The man who acquires some wealth can set aside money for problems that ARE going to come. In our society, if you own a car or other mechanical item, you are assured that a breakdown of some sort is in your future. If you spend everything you have - you will not have anything set aside for this difficulty. The wise man acquires wealth for this very purpose. He puts money away for the repair and replacement of such items. Therefore when a difficult time comes, he has money for these things. The poor man often is ruined by such situations. He does not know what to do and often sees ruin come to his financial picture because of debt he obtains seeking to fix or replace things or he just has to do without, which could be a very problematic hardship. Wealth can be a protection for us.
The problem with this proverb is that one might think wealth is the ultimate protection. Therefore we must gain wealth however we can. Such thinking is ungodly - and will lead to ruin, if not now - then in eternity. Therefore we have a clarification in the next verse. We are told that the wages or income of the righteous is life - which the income of the wicked is punishment. If we are seeking righteousness - a life that pursues God and desires to do what God says is true and just - we will be blessed. We may not have a tremendous amount of money - but we will have what is necessary at the end of the age. We will have life! The wicked though, however rich they may become, have a serious problem. Their income will be punishment. Thus a man may be tremendously wealthy by all outward appearances - but he may be dirt poor in spirit. The rich farmer in the gospels had enough to tear down his old barns and build new ones to fill with even more earthly riches - but the very night his soul was required - he was found destitute.
Remember that wealth and riches are defined in a number of different ways in Scripture. They may be physical wealth - or they may be spiritual riches in Christ Jesus. It is wise to remember that to be physically wealthy according to James is to be put in a humble place by God. It is difficult for an earthly rich man to enter heaven - because he has a bad tendency to trust his riches. To be poor is also defined different ways. Whereas it may be a bad thing to be financially poor - it is a blessed state to know that we are poor in spirit. Realizing these things will help us better define true wealth and true poverty.