Bro, since you brought up passive income, thought I will share one version of it.
Passive Income & Opportunity Cost
Though passive income is usually defined as initial hardwork yielding income stream for years to come. Typically as you pointed out they are things like rental income and also tiered periodic commissions from Insurance / mortage sales, royalties, dividends from shares etc.
Here is another angle. Do you know why sr executives in banks, blue chip companies etc do not quit and run their own companies. Here is the reason why and despite having large responsibilities
1) No personal monetary risk or commitment as they work for a large firm or MNC
2) There travel & entertainment expenses are sometimes much more than the Annual income. Compute 47 business trips a year, flying Business Class costing $9K USD per trip for air fare and $2000 USD for hotel bill/ tips. local transport for a typical 3 day stay, and opportunity to sight see, meet people from various cultures and going to amazing places, take holidays as side trip. We are talking about $517K USD per year in T&E. All company expenses with taxes.
3) Guess the number of free tickets for family in 1 year to the furthest place on earth.
4) Staying in the comfort of your airconditioned office and just using your brain power to delegate work to staff, provide directions and make strategic decisions.
5) Bonuses up to 70s.
Guess what happens when you are doing all the above and in a line of work that you love? And I am not talking about Sr Management of Companies that travel 1st class. Its just middle management in an MNC that has a global responsibility.
Take another example but this time a professional such as doctor or Engineer who runs his own business but gets paid travel from pharmaceutical companies and large vendors to attend seminars and conferences at exotic locations. Own expenses that are tax deductible.
Some of the best and brightest work for the best companies around the world. That is also the reason why people struggle thru schools, universities pursing degrees and burning the midnight oil.
And its not about money. It about opportunities to travel, meet interesting people, use the huge resources of your company to invent things, build systems, introduce new ideas and help change the world for the better.
Thats opportunity costs. Ever worked for Barclays, GE, Chase etc.
You call do all the above and still have quality time with your kids. Your kids will be boasting about you during the Career Day talk in school, your kids will travel to the most exotic places on god's green earth from the frequent flyer points. They will eventually go to the best schools in the world.
These people would have also invested their bonuses and income in properties, shares, and other people's business and all these are passive income.
The world is your oyster and the best thing that you can do is make sure your kids understand that and go on to realise their full potential.
The majority owner of Fish & Co, the successful seafood based chain of restaurants in Singapore retired as an executive with SIA and has migrated to S Africa to retire on a large plot of land. He has seen the world over 30 years and its only a local company. He does not run the business but his minority partner does. His income is passive income from start to finish. Only looks at the annual P&L.
Just a perspective.