If you'd like some interesting reading, take a look at the traditional Catholic analysis of usury: https://zippycatholic.wordpress.com/2014/11/10/usury-faq-or-.... According to this modern summary, anyway, any interest-bearing loans that are personally guaranteed (such as credit card loans or student loans) are immoral. However, investment is permissible, as are collateralized loans (either against property, such as a house, or against a corporation, which is a sort of property); however, in the event of default, it would not be permissible to go after the corporation's owners to recover the rest of the loan (although if the owners illicitly withdrew money from the company they'd still be liable for fraud).

EDIT: Submitted at https://news.ycombinator.com/item?id=21032154