This thread has focused on the earnings side of the equation, which is important.
In my case, I focused on the cost side; my long term goal was to minimize recurring costs because if the money went south, I might still be able to manage. Homelessness will do that to you...
Housing around here is expensive which also means it could be a good investment. I bought the worst house in a strong zip code and proceeded to fix it up and pay it off. I also installed solar and a tankless water heater, again with the goal of minimizing recurring costs.
I live dirt cheap in a well patrolled and kept area. It's great. And let's just say the investments have far exceeded my expectations.
I guess that's because I feel very confident in my cost management, so I have not made it a focus. However...
-I owe $250K or so on my estate. I have a 2.99% 20Y fixed loan, 14 years of which remaining, on my solar array, which cuts my electric bill nearly to 1/3 of what it was, even with my EV. The panels are rated for 30Y production, and warrantied as such (80% efficiency retention by then).
-The house is in excellent repair, and I carry a home warranty that will replace my HVAC when it dies, which is by and large the greatest projected expense other than a roof, as I project mine has 20% life left, although it looks good.
-I do still owe on my car, but it is an EV, and once paid off should have nearly zero operating costs. This will allow me to drive for VERY cheap when you throw the solar panels into the equation. While it won't last until retirement, it WILL make putting more money away or paying other things off much quicker and easier. I also happen to get joy from it, so that makes it priceless.
-I have a well.
-I chose an area with low costs. Property tax on my estate is $1200/year, electricity has been 12 cents/kwh delivered for 20 years and counting, roughly. Property insurance is very affordable with my mortgage coming out to under $1600/mo including escrow (taxes and insurance included in mine).
Overall, my fixed costs once everything is paid off, should be about $10K per year. ($4K insurance and taxes on the estate, $1500 home warranty, auto insurance is too variable to project and those prior two don't take inflation into account, hence the under-shooting of the ind. actual costs vs. the overall $10K projected.). After age 65, home owners here pay $1100 less on property taxes, which should almost wipe mine out.
This of course neglects food and clothing costs, but I intend to stay in an EV, so there is that aspect. Overall, you can see costs are supremely low, even before things are paid off, except for the sake of my car, which I did go hard in the paint on, because some things are worth more than money to me, and after an entire trash shift, it perks me up a bit to be walking out to something I actually want to get into and drive away in.