On one level, I get that: it is economically sensible to play the landlord role, even at a small scale. And in a lot of ways, you're doing something really important. You're providing someone with a place to live, one that they don't have to worry about taking long-term care of. You've decided that you're going to be a long term care-taker of this home. Assuming you're a good landlord, you really are doing some good for the world.
But would you really be "dumb" if you did things differently? Or would you be following a different set of economic values? Seriously, think about that. I challenge you to rethink your "smart vs dumb" idea. It's "smart" to drive and rely on a car. But on another very important level, it's also incredibly foolish, a.k.a. "dumb".
And I'd argue that what you and your renter have done is also pretty "dumb". Why? Because you and your renters are paying the bank that much for a house. The cost of building a new house is much less. This is an old house, but the bank said "this house is actually worth more than a new house, because you can simply pass the debt onto someone who doesn't have the option of buying a house at this moment, even though they urgently need a place to live". The house itself probably isn't inherently "worth" that much: it takes a lot of work to keep up an aging house. Yet all of this rent money is harvested from the occupant's time/earnings/savings: money that could be invested in the house gets sucked into some exponential function that translates to the bank taking thousands of dollars a month from your renters. Since the bank is so "helpful", you get to keep a very small amount allowance so that you can do repairs/profit. Of course, in the end you'll "own" the house, you'll have paid off your mortgage. Or maybe you'll sell it to someone else, who will enter into a similar agreement with the bank. Regardless, by the time someone has paid off the mortgage, banks will have gotten off with something in the range of 0.5-5x the entire inflated value of the house just for handling sacred paperwork. To me, that's DUMB.
This kind of thing is technically forbidden in Islam, Judaism and arguably Christianity, but not in the USA.
By the way, I'm right there with you in doing dumb stuff like this: I'm a renter.