Though it requires a huge up-front investment (well, at least 20%), real estate is awesome, because it’s (usually) pretty stable, and it’s a triple-whammy: you make money by leveraging a bank’s money, you can rent it out with almost no work at all day-to-day, and the value of the underlying asset INCREASES. This is why so many people flock to AirBNB to rent out their apartments when they’re going on vacation, too. It’s pretty passive, you don’t have to own the asset, and you just hand over keys and hire a cleaner before/after. The value of your apartment is untouched. By contrast, imagine buying a plane and renting it out to people for tours — you pay tons of money to maintain it, and after 20 years, it’s value is almost nothing. The exception is if you can manage depreciation and somewhat automate the value-delivery. If you have an expensive tool (like a 3D printer) and charge people to come over to your house and print things on your 3D printer, it’s pretty passive for you to answer emails and open the door, so I give it a “Semi to yes” for passivity.
* I use Personal Capital to track all my finances in one place. It’s much easier to use their free software to follow 28 accounts on one platform than to log into various accounts to check my balances. They’ve also got great tools for x-raying your portfolio for excessive fees, recommending a more optimized asset allocation, and planning for retirement with their Retirement Planner.