If you have often turned 20,000 into hundreds of thousands in a business, I'd say you have an uncommon knack for that business(or multiple businesses).
I agree RE is a business, one with fairly low barriers to entry, but with high barriers to success.
I have only ever really invested time in my business, I don't see opportunities that would require capital, at least I don't see opportunities that I want to pursue.
I think Real Estate success is very much determined when you 'buy', and really before that, when you analyze. So, that's where your uncommon business sense and abilities could make you successful enough in RE to make it worth it. If you are able to reserve your capital for only the best deals. Now how much time will it take to find them? and how else could you profit using the same capital and time? only you can figure that out for yourself.
So, I'd say there are 5 ways:
leverage
tax advantages
'buying at the right price based on skilled, sound analysis'
rehabbing/identifying 'best use'
deal-making(wholesaling, bird dogging, note buying/selling)
Some of these can be achieved passively:
leverage + tax advantages
But even those require the work up front to at least identify, analyze and purchase - and set up management
And of course: being your own PM, rehabbing project management(or hammer swinging), and all the deal-making options take constant investment of time.
Deal-making is a non-starter for me, I can trade hours for dollars at a high rate in my regular business.
Buying at the right price is not a skill I believe I have, I could learn it, and I read here a lot, but I am consistently surprised by how many things the experienced people on here point out that I would have missed or have never thought of.
So that leaves me seeking leverage and tax advantages but frozen from buying due to my fear of becoming a 'learning example for ohters' by overpaying.
So, like you, I suspect, I focus my efforts on my 'other business' and I keep my capital in the stock market. I get my tax benefits by doing massive 401k contributions because I work for my own corporation that has very generous matching policies, and also employs my wife who is the beneficiary of those same generous profit sharing 401k contributions.