“get a 30 year mortgage and pay it off early by doubling payments.”
We basically did that. On the first house, made two payments a month. One on the loan, and one applied to the principal. After that we were able to pay cash.
For years we lived WAY below our means. It wasn’t fun, but in the big picture it has paid off.
The key to retiring early and comfortably is the ability to reduce spending and save money.
What one invests in is important but not nearly as important as the ability to save the money in the first place.