...
No, making money through usury is unethical. At least if we are going by typical biblical ethics, otherwise all we are left with is personal opinion. In which case, screw your ethics.
The Bible has a much wider interpretation of "usury." Religious law, both Jewish and Christian, prohibits lending money with interest -- that's usury. Which pretty much precludes "making money by having money" (though there's nothing there about deflationary currencies, which could be seen as making the holder wealthier).
There's very interesting theological loopholes/acrobatics that allowed both Jews and Christians (and Muslims) to make money by lending money.
For a Christian who can't lend money and charge interest (per Jesus' teachings), there's nothing preventing him/her from charging a preset commission/fee for lending money to someone and including the fee in the repayment or by doing something like this for example:
You want a car but can't afford it. I have lots of money, enough money to buy the car you want in fact, but since charging interest rustles my lord's jimmies, I have no incentive or security in lending you money. To get around charging interest and still make it worth my while - here's what I do: I'll buy the car for say $5000, sell it to you for my asking price of $5500 (10% above what I bought it for), but since you don't have $5500, I conveniently have exactly $5500 for you to borrow from me which you agree to pay back. Wam bam, no interest, no usury per new testament definitions of usury.
For a Jew on the other hand, (in addition to the one mentioned for Christians) there's a different loophole which resulted in a lot of awful stereotypes. Usury was forbidden in the old testament....as it applies to your brother, or your people, or in other words, other Jews...as stated here Deuteronomy 23:21 - it's perfectly okay to lend with interest as long as you're not doing it to another fellow Jew. I'm sure you can connect the dots as to what happened when Jewish communities were the only ones allowed to offer straightforward banking services to people who needed them but couldn't because their big dude in the sky said "Nah brah, sorry".