Brian it sounds like you've done your homework! 🙂
After military service I had an engineering job at Boeing. After a while I moved from an apartment to a rental house that had an option to buy at very attractive terms. When the option came up I looked around for alternatives, such as getting a duplex where I could make expenses by renting out the other half. Well, I found a good deal on 9 units and took over the existing contract. Lot of work and learning the ropes...
After few years I took a voluntary layoff at Boeing, sold the apartments and used the proceeds to fund a 25 unit apartment bldg. I took a real-estate contract on the previous apts and earned interest for 20 years... which helped at the new apartments as it gradually became more profitable. Large fixed costs, substantial variable costs for maintenance and replacements, steadily increasing income.
Also, shortly thereafter, I started an investment program by taking Money Magazine's suggestion of 10 best investments to start with, going with small amounts of each suggested issue. That was fun and interesting, and the investment grew. After 35 years I sold the 25 unit building and put the proceeds, along with the older investments, into a managed investment account at a financial institution. I concentrated that conversion toward income-generating investments that provide a steady reliable income.
One thing to consider is keeping large debt, like a house or new car, rather than paying them off even when easily possible. Once the apartments were sold we bought a house at about 4% interest. It would be nice to pay it off, right? Yes, in a way, but the investments that we would cash in to pay off the mortgage provide around 7% return. We'd be losing the ~3% difference if we did that. Not too smart! Just need to keep the debt manageable... and pay off credit cards every month, etc....
Best of luck and good fortune!