How do you get rental income without buying real estate? You have to invest before you can reap rewards.
The percentages are the same for everyone, of course a higher investment results in a more comfortable income.
The 1M+ steem on the curangel account are delegations from people who already use the service for their investment, the individual amounts differ widely from person to person.
Which asset class you trust more in terms of appreciation, and how your tax man handles them, is not part of this post. And you won't get into the realms of 8%+ p.a. with real estate, especially after substracting costs and time (because, as stated, it's not passive).
Of course you must invest the cash, but buying at the right price in a good market, creating a positive cash flow. Then hiring a good property manager, this creates passive income long term.
So why's half of your previous comment about the necessary investment and whales on steem?
It depends on each individual investors risk profile and future expectations what to invest in. And putting all your eggs into one basket is generally not a good idea. If you think the upside potential of real estate is higher than steem's, or if you are shy of the risk steem naturally includes, that's up to you. Speaking of a "best" seems weird.
The good property manager to make it passive cuts even deeper into your profits. Getting half the APR you get here would be exceptional, not considering asset value. The risk is lower, but that's the only thing "better" about it.