It is certainly a subject the Church has been lax on in presenting clear teaching. Search around on web sites and find no clear answers. I take my key from Belloc, and apply it to a more modern understanding of money and it’s time value.
First if all, differentiate between a productive and non-productive loan. A business loan vs a consumer loan, if you will. Usury doesn’t really apply towards loans to an ongoing enterprise. I think it fair to count home mortgages as productive loans, as they are an appreciating asset.
In general, usry applies to non-productive loans, ie consumer loans. Now, most will say that a reasonable rate is ok, and only hugh rates are userous. In general true, but I would say only the rate that takes into account the time value of money plus a small added amount to accommodate risk of default is allowed. But for sure, any interest rate that make repayment difficult is always userous.
We have a economy that has way too much usery built into it, eg payday loans, high penalty credit cards, pawn shops, etc. As I said, the Church needs to provide clarity.
