It is not a sin to be rich, God grants us riches! It is sinful to be MISERLY. If you do not give to your fellow man what God gives to you, then that is sinful.
That’s O.K.
But understand the spiritual things. Having money is a terrible burden. Money and the desire for money can occupy all of your thoughts. I’m not counting the rich who delight in the pleasures of this world. I’m just saying from experience what having a lot of money can do to a man. If a man spends his day counting his money, he can not serve God. No one can serve two masters; for either he will hate the one and love the other, or he will be devoted to the one and despise the other. You can’t serve God and mammon. Mt. 7:24 His mind is set on the things of this world, to get more (for those who live according to the flesh set their minds on the things of the flesh). The mind that is set on the flesh is hostile to God. Ro. 8:7
But there’s more. To live one must have water; we thirst for the words of God. To understand we must hear first. The Spirit has to lead us to water. But understanding comes from God. Even so, the man hears the word of the kingdom and he understands but the cares of the world and the delight in riches choke the word and it proves unfruitful. The word is close to your lips. It springs from the heart. But if the desire of your heart is money, then the word can’t get out. It doesn’t come to mind. It doesn’t leave the mouth. So what was sown proves unfruitful.
And even worse you might forget God and begin to live like everyone else instead of seeking, finding, entering; for the door is open. Don’t wait for the day of judgment to enter the kingdom, like those who will say they did many works in his name. Enter, find pasture. For when the door is closed many will knock and they will not be able to enter.
Luke 13:25 RSV
When once the householder has risen up and shut the door, you will begin to stand outside and to knock at the door, saying, 'Lord, open to us.' He will answer you, 'I do not know where you come from.'
Revelation 3:20 RSV
Behold, I stand at the door and knock; if any one hears my voice and opens the door, I will come in to him and eat with him, and he with me.
Then again, the man may enter and find pasture. He eats and drinks, but the desire for riches chokes the word and it proves unfruitful. I hope my words prove fruitful.