Unethical but not usurious (according to the blog). The first point is more so about if the borrower defaults and can't pay back. It one thing to have nothing, it's another thing to owe money while also having nothing.
I wouldn't exactly call it "having nothing". All those months (or years) you paid on the mortgage, you had a place to live, and once you defaulted, you still got up to a year of free rent, you could say. It's actually pretty rare, or at least it was in my experience, for the representatives of the lender to come along with a moving crew (and perhaps a constable or sheriff), and carry the contents of the house out and put them on the street, with the family being kicked out and put on the street as well. More common is that the delinquent borrower has long since abandoned the house, sometimes hasn't even opened their mail or has thrown it away (I spent a massive amount of time doing skip tracing, sometimes I felt like a cubicle-rat version of Dog the Bounty Hunter), and the actual seizure of the house is relatively painless. Lenders end up having to pay for things like winterization and lawn maintenance during the vacancy period out of their own pockets, not to mention taxes and insurance. They don't want the home to be sold in a tax sale, nor do they want to have the house burn down and be left only with land. We even had one case where we were able to monitor water usage, and caught the borrower up in a lie when he claimed he hadn't been living there. I couldn't make up some of these stories if I tried.
As I tell my son, it is the rare 18-year-old who owns a home free and clear, so recognize that, and be thankful for it, or rather, thank your dear grandpa who made it possible. (And keep your taxes and insurance paid current.)