See also: http://judaism.is/usury.html
A lot to unpack here, I've put a shortcut to it on my desktop and will read in more detail later. Usury is one of those things, really unique in my adoption (a more accurate term that "conversion" in my case) to the Catholic Faith, at which I've been totally at loggerheads with myself all these years --- how can money be the one and only thing you can't "rent", but on the other hand, how could the Church teach against it at one point, and now be more or less neutral on the matter, unless it is "biting" interest? That's an argument that dissident Catholics use, to maintain that the Church will one day change her teaching on contraception. Again, I'll read into it.
Two more notes, leading me to think that this is yet one more good thing my recently departed father, who left all of us in good shape financially (not wealthy, just in good shape) through a lifetime of hard work and sharp business sense, can give to all of us, including this forum. (He once asked me, "that Catholic stuff you do on the internet, is there any way you could make money off of it?"
--- he had a hard time understanding why a grown man would invest time in something with no money coming from it, that was just him, and I guess I can start complaining about it, when I forget how he left us with two nice homes and no mortgage on either one.)
First, there is always the option of buying a duplex, or a large home that has been made into a duplex, renting out one-half of it, and living in the other half. That's what we did when I was growing up, big circa-1900 foursquare home in our small town's park neighborhood, beautiful setting, close to downtown. He bought it in 1967, we rented out the upstairs, and we lived in the downstairs. The rent from the upstairs basically paid the mortgage on the house. When we got a little more on our feet financially, we took down the door separating upstairs from downstairs, and took the whole house, but for the first few years, we lived basically mortgage-free. He also bought other duplexes, I don't believe we ever had but one at a time, and used the rent from those to pay the mortgages. Collecting rent was sometimes a challenge. It would be even worse now, when the laws are heavily in favor of the tenant. Just because you don't pay your rent, doesn't mean that the landlord doesn't have to pay the mortgage on that house. It's all cash flow. He bought one other duplex, down the street, flipped it, and made enough profit to pay off our own home. He went down to the bank, said "I want to pay this off in full, how much do I make the check out for?". They said "you can't do that" --- I guess it was one of these old-fogey small-town banks that didn't deal with institutional investors, and was reliant upon people taking 30 years to pay off, with the interest stream in the meantime --- and he told them he had the money, and wanted to pay it off. He paid it off that day. At that point, they really didn't have much of a choice but to take his check.
Second, when you think about it, when you rent, you are indeed paying interest --- interest on the landlord's mortgage. Not many people have the luxury of ideological purity --- "I'll seek out only rental properties that are paid for, so I won't have to pay usury, and be part of the interest problem".