Psalm 15 asks “who can dwell with God?”, that is, “who will be saved and be in God’s presence forever?”.
The Psalm then lists various attributes about the righteous ones who will be saved. As Christians, we look to Jesus as the one who perfectly lived according to this. He in turn shares his righteousness with his faithful. These attributes then also are a guide for how we ought to live as Christians
Verse 15 is not condemning banks or other lending companies necessarily. Rather, it is addressed to us as individuals. Do we take advantage of those in need? This often is the case in lending money, with the hope of gaining much through interest. Similarly, do we allow ourselves to be bribed or influenced by those with power, while the helpless are further taken advantage of?
Our Lord Jesus paid our debt of sin freely, with no bribery or interest involved. We, too, then should have grace with each other, lest we be caught like the unforgiving servant Jesus spoke of in a parable (Matthew 18:21-35).