The average yearly return of the S&P 500 over the last 30 years is almost 10% a year, so if instead of investing in the stock market, you choose to be a landlord whose yearly profit is 4%, you’re a humanitarian donating 6% of the cost of your apartment to your tenant every year.
I’m exaggerating because the average rise in real estate values is 6% so such a landlord actually gets about the same return as he would get from the stock market, as long as he never has a bad tenant and doesn’t mind his money being locked up in real estate.