You have maintenance/depreciation and insurance expenses, and have the opportunity cost of whatever capital you have tied up in the property.
I think home ownership is a great choice for many and I own slightly more than 50% of the house we live in [the bank owns the rest right now]. But there are very real costs to ownership and they don't stop at property tax IME.
You'd have to design and build a custom home way outside of the designs considered normal for the market to make it significantly more (but not completely!) maintenance-free in the long run, at a significant increase in construction cost. But then you've subjected yourself to another hidden downside: the more strange/custom/expensive a home is, the less liquid that home will be on the market if you decide to sell later. A home that's awesome to you but not-awesome to 95% of the market doesn't move. And if you're stuck with it and it's a significant chunk of your wealth, then you can't move cities for that new job or whatever.
you mention hvac. i will not have hvac. you mention repainting, i dont have to paint if i dont want to. you mention flooring, my floor is concrete. you mention sheetrock, the sheetrock will be fine.
all of this is well within code and well within what i would call normal. but i hope that people will find it strange or un-buyable because that would reduce the market value of my improvements to the land and therefore lower my property tax. i am aiming to get the lowest operating cost possible, and having a home that has low liquidity actually greatly helps that. not every home has to be a flipping scheme.
I chose our current house in part because of the slate roof and unpainted structural brick exterior (both very low maintenance). I admire your search for low operational cost housing; I hope that your eventual house comes out just as low cost as your optimistic projections above.
Example: Did you ever have to run out to your local hardware store to pick up a small widget (e.g maybe a few screws of specific size, length, etc.) late at night...only to find that the store doesn't stock that exact type of widget that you need...the hardware store doesn't stock what you need because most of their customers buy typical stuff, and your needs are too long-tail. Let this seemingly little annoyance happen to you a couple of times before you start hating that your home is "one-of-a-kind". And then you begin to buy parts/widgets that cost too much - either because you have to drive all over the place (and maybe you buy an extra widget to avoid repeated future searches) or because the widget costs a premium to begin with...Or, worse, you begin to use 3rd party repair providers - because they regularly stock weird widgets like what you need - and then you're paying them a slight premium to repair (which maybe you could have repaired if you only had the freakin' part/widget)!
Or...What if your property has trees on or near it...and your area goes through seasonal changes where the leaves fall? Maybe you care (or don't) about raking up leaves...Or, maybe your town has ordinances - or your community has local "rules" - about you needing to keep your land "neatish", and then "forces" you to clean up your area through fines, etc. Here again, you can pay someone else to rake/pick up the leaves, or you can do it yourself. Bam, you pay one way - either time or money.
There are countless other examples - no matter the home or location - where owning a home requires investments in time or money, and often both. And, if anyone tells you that "they love working on the house, or cleaning up their yard"...and that it doesn't count as money or time used up, then managing their home is basically their hobby...and hobbies cost money and/or time.
What happens when a hurricane rolls through and rips off your roof or there's a fire?
2. Don't build homes out of flammable material.
3. Use the money you would've spent insuring a house on repairing it.