Hypothetically: $1mil after tax paid cash to use for a share portfolio.
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If margin lending, you can include margin call, and payment of interest.
If you've got $1m after tax, then no margin call or interest. Are these the same scenario?
Short answer, yes $1m clear =~ $70k pre-tax recurrent. Then pay tax at whatever the marginal rate is for $70k (I have no idea). It'll be more than $50k after tax, if that's your first mil.
Even better, if done even slightly properly, your $70k will be "inflation immune" (your other risk assessments are spot on).
Well done to be in this position at that age !
But, please consider: is $70 k/pa enough? If you are 60 years old and keep yourself happy by snipping discount coupons from the NRMA magazine, then perhaps so. But at 30, you're gonna want to have a boat, travel, have fun, etc. You'll need way more than $70k unless you're happy to be the king of the caravan park and dedicate your life to relish in the avoidance of further work. I would suggest you sock that mil away in appropriate investments, and get to work on the second one. Retire when you're 40, with 3 mil and $150k/pa inflation immune. Much better. Don't forget to buy a place to live somewhere along the way.